Istanbul is a city that has been shaped by centuries of history, culture, and religion. It is a melting pot of civilizations, a bridge between Europe and Asia, and a place where the past and present coexist. One of the most significant periods in Istanbul’s history is the Byzantine era, which spanned from the 4th century AD to the 15th century. The Byzantine Empire left a lasting legacy on Istanbul, evident in its magnificent architecture, religious art, and imperial grandeur.

Old Byzantine Churches and Monasteries

Hagia Sophia

Originally built by Emperor Justinian in 537 AD, Hagia Sophia was the largest Christian cathedral in the world for nearly 1,000 years. Its vast dome and mosaics exemplify Byzantine architecture at its peak. After the Ottoman conquest, it became a mosque, and today, it functions as both a mosque and a museum.

Hagia Eirene (Aya Irini)

Hagia Eirene is one of the oldest churches in Istanbul, originally built in the 4th century during the reign of Emperor Constantine, making it older than Hagia Sophia. Unlike many Byzantine churches, it was never converted into a mosque. Today, it functions as a museum and concert hall.

Hagia Eirene is significant for its role as the first church in Constantinople and one of the few remaining structures that retains its original Byzantine Christian form. The building has a large dome and apse but is devoid of the rich mosaics that adorn Hagia Sophia.

The Myrelaion (Bodrum Mosque)

The Myrelaion Church, now Bodrum Mosque, was built in the 10th century by Emperor Romanos I Lekapenos. It served as a private imperial church attached to his palace. The church has a cross-in-square plan and retains much of its original Byzantine structure. The underground cistern beneath the building adds another layer of historical significance to this site.

Zeyrek Mosque (Pantokrator Monastery)

Originally the Monastery of Christ Pantokrator, the Zeyrek Mosque is one of the largest Byzantine religious complexes in Istanbul. Built in the 12th century during the Komnenian period, the monastery housed three churches and was used for imperial ceremonies and burials. Converted into a mosque in the Ottoman era, the building still retains many elements of its Byzantine architecture, including its massive dome and original mosaics.

Aya Sergios ve Bachos Kilisesi (Küçük Ayasofya Camii)

Aya Sergios ve Bachos Church, also known as Küçük Ayasofya Camii, was built between 527 and 536 AD by Emperor Justinian I and Empress Theodora. It served as a prototype for Hagia Sophia, reflected in its architectural design.

According to legend, Justinian dedicated the church to Saints Sergius and Bacchus after receiving divine protection from them during a conspiracy. Today, it is a mosque, yet still retains its Byzantine features, making it a significant historical site and part of UNESCO World Heritage.

Monastery of Stoudios (İmrahor Mosque)

Founded in the 5th century by the Roman consul Stoudios, the Monastery of Stoudios was one of the most important monastic centers of Byzantium. It played a key role in the religious and intellectual life of the empire. Although heavily damaged, its remnants—now known as İmrahor Mosque—are still visible today.

The Church of Theotokos Kyriotissa (Kalenderhane Mosque)

Located near the Aqueduct of Valens, the Theotokos Kyriotissa, now Kalenderhane Mosque, dates back to the 12th century but includes earlier structures, such as a 4th-century bath and a 6th-century basilica. The church’s architecture reflects a complex history, incorporating various layers of Byzantine building techniques.

It was converted into a mosque after the Ottoman conquest in 1453 and has undergone several restorations. Despite these changes, it remains one of the lesser-known but architecturally significant Byzantine sites in Istanbul.

Monastery of the Theotokos Pammakaristos (Fethiye Mosque)

The Monastery of the Theotokos Pammakaristos, built in the 12th century, was one of the most significant Byzantine churches in Constantinople. After the city’s reconquest in 1261, it was restored by Michael Tarchaneiotes and later became the seat of the Greek Orthodox Patriarchate.

In 1587, the church was converted into a mosque, known as Fethiye Camii. While its parekklesion was once famous for its stunning mosaics depicting scenes from the life of Christ and saints, these mosaics are no longer visible. The mosque has since been repainted, and the mosaics were removed or covered due to the building’s renovation.

Church-Mosque of Vefa

The Church of Hagios Theodoros, now the Vefa Kilise Mosque, is another important Byzantine relic in Istanbul. Likely built in the 11th century, it was converted into a mosque during the Ottoman period. The church is notable for its cross-in-square architectural layout, a hallmark of Middle Byzantine church design.

Chora Church (Kariye Mosque)

Located in the Edirnekapı neighborhood, the Chora Church (now Kariye Mosque) is famous for its stunning Byzantine mosaics and frescoes. Built in the 4th century, it was extensively renovated in the 11th century. The mosaics depict biblical scenes with incredible detail and color, showcasing the height of Byzantine artistry. After the Ottoman conquest, the church was converted into a mosque, but much of its Byzantine art remains intact.

St. George’s Cathedral (Church of Saint George)

St. George’s Cathedral, located in the Fener district, is the seat of the Ecumenical Patriarchate of Constantinople and remains the spiritual center for Eastern Orthodox Christianity. Though the current structure is relatively modest compared to the grand Byzantine churches, its significance is immense. Since 1601, the cathedral has housed important relics, including those of St. Gregory the Theologian and St. John Chrysostom. As the headquarters of the Greek Orthodox Church, it remains a vital religious site.

Hagia Theodosia Church (Gül Camii)

Hagia Theodosia Church (Gül Camii), once a Byzantine church, was converted into a mosque after the Ottoman conquest of 1453. It retains much of its original structure, including the dome, but now serves as Gül Camii. Today, the area around it hosts cafes and workshops.

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Hippodrome of Constantinople

Though little remains of the Hippodrome, it was once the social and sporting heart of Byzantine Constantinople. Built by Emperor Septimius Severus and expanded by Constantine, the Hippodrome hosted chariot races and political events.

Obelisk of Theodosius

Originally from Egypt, the Obelisk of Theodosius was brought to Constantinople by Emperor Theodosius I in the 4th century. It stands at 20 meters tall and is covered with hieroglyphics. It is located in what was once the center of the Hippodrome of Constantinople.

Serpent Column

Also located in the former Hippodrome, the Serpent Column was originally part of a sacrificial tripod at Delphi and was brought to Constantinople by Constantine the Great. This bronze column is notable for its age and the symbolic victory it represents over the Persians in 479 BC.

Byzantine Walls, Towers and Fortresses

Theodosian Walls

The mighty Theodosian Walls protected Constantinople for centuries, built in the 5th century under Emperor Theodosius II. These walls were a critical defense against invasions, including the famous siege by the Ottomans in 1453. Stretching across the western edge of the old city, the walls still stand, offering a glimpse into Byzantine military engineering.

Genoese Tower in Galata (Galata Kulesi)

Though the Galata Tower is primarily associated with the Genoese in the medieval period, its foundations date back to the Byzantine era. The original tower, built during the reign of Emperor Justinian in the 6th century, was part of the fortifications of the Byzantine city. The current structure was rebuilt by the Genoese in the 14th century but still stands as a testament to the layered history of the city.

Yoros Castle

Yoros Castle is a Byzantine fortress located at the confluence of the Bosphorus and the Black Sea, near the village of Anadolu Kavağı. Built in the early Byzantine period, it once guarded the entrance to the Bosphorus. The strategic importance of Yoros is reflected in its robust design, and the castle was repeatedly contested between the Byzantines and the Genoese.

Maiden’s Tower (Kız Kulesi)

Maiden’s Tower is a key Byzantine structure located on a small islet off the coast of Üsküdar. Originally built in 408 BC as a customs station for ships entering the Bosphorus, it evolved through the centuries. During the Byzantine period, it served as a defensive tower. The structure was rebuilt several times, including a wooden version fortified by stone walls in 1110 AD.

The tower has been used for various purposes — watchtower, quarantine station, and lighthouse. Its historical importance is reflected in its strategic location. The tower is also linked to several legends!

Blachernae Walls

The Blachernae Walls were an extension of the Theodosian Walls, built during the 12th century to protect the Blachernae Palace area. They were stronger and higher than the older Theodosian Walls due to the palace’s strategic importance. This section was crucial in defending the northwestern part of the city, where the Golden Horn meets the walls.

Blachernae Palace (Tekfur Sarayı)

The Blachernae Palace, now known as Tekfur Palace, is one of the few surviving Byzantine palaces in Istanbul. Built in the late 12th or early 13th century, it was part of the larger Blachernae complex located near the city’s Theodosian Walls. The palace was used by Byzantine emperors and later by the Ottomans. Though much of the structure is in ruins, restoration efforts have brought parts of it back to life, and it now serves as a museum.

Yedikule Fortress (Fortress of the Seven Towers)

Located at the southern end of the Theodosian Walls, Yedikule Fortress was originally built by the Byzantines as part of the Golden Gate, the ceremonial entrance to the city. After the Ottoman conquest, Sultan Mehmed II expanded it into a fortress. It served as a treasury, prison, and military garrison over the centuries. The massive towers and robust structure make Yedikule one of the most impressive medieval fortresses in Istanbul.

Byzantine Cisterns & Aqueducts

Basilica Cistern

Constructed under Justinian I in the 6th century, the Basilica Cistern is an underground marvel. Used to store water for the city, it features rows of columns, many repurposed from earlier structures. Two Medusa head carvings found within are iconic, symbolizing Byzantine artistry.

Cistern of Philoxenos (Binbirdirek Cistern)

This lesser-known underground structure, also called the Binbirdirek Cistern, was built in the 4th century. It is the second-largest cistern in Istanbul after the Basilica Cistern. The columns inside the cistern are notable for their different capitals, reused from various older Roman structures, reflecting the Byzantine practice of repurposing materials.

Aqueduct of Valens (Bozdoğan Su Kemeri)

The Aqueduct of Valens is one of the most prominent symbols of Roman and Byzantine engineering in Istanbul. Built around 368-375 AD during the reign of Emperor Valens, the aqueduct was part of a sophisticated water supply system for Constantinople. Its structure, spanning 920 meters in length and 30 meters in height, still stands impressively over the busy Atatürk Boulevard.

The aqueduct operated for nearly 1,400 years, surviving both Byzantine and Ottoman eras. Today, it remains a key historical landmark and a favorite photography spot, particularly at night when it is illuminated.

Cistern of Gülhane Park (Gülhane Parkı Sarnıcı)

Hidden within Gülhane Park, this underground cistern is believed to have been part of the water transport system built during the Byzantine era, possibly as early as the 4th century. Measuring 17.37 x 12.37 meters and supported by 12 marble columns, the cistern offers a glimpse into the infrastructural achievements of ancient Constantinople.

Byzantine Columns

The Column of Constantine (Çemberlitaş)

Erected in 330 AD to commemorate the founding of Constantinople, the Column of Constantine (also known as Çemberlitaş) is one of the most important monuments of Byzantine Constantinople. The column originally supported a statue of Emperor Constantine as Sol Invictus, the unconquered sun god. Standing at 35 meters, the column has suffered damage over time due to fires and earthquakes, but it still dominates the area near Sultanahmet.

The Goths’ Column (Gotlar Sütunu)

Located in Gülhane Park, the Goths’ Column is one of the oldest surviving monuments from the Roman era. Likely erected in the 3rd century AD, it commemorates a Roman victory over the Goths. Standing at about 15 meters high, this marble column lacks detailed decoration but is significant for its age and the historical events it celebrates.

The Column of Marcian

Located in Fatih, the Column of Marcian was built in the 5th century in honor of the Emperor Marcian. Standing on a high pedestal, the column features a Corinthian capital and once supported a statue of the emperor. While the statue is long gone, the column remains an important relic from Constantinople’s imperial period.

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