- Ancient Chalcedon in Modern Kadıköy
- Reading the Ruins of Ancient Chalcedon
- Searching for St. Euphemia Basilica in Chalcedon
The history of Chalcedon often centers on the Basilica of St. Euphemia, the site of the Council of Chalcedon. Built over the grave of Saint Euphemia, this famous church has vanished from view, leaving behind one of the city’s greatest archaeological puzzles. Where did it stand? Historical sources, topography, and recent discoveries offer several compelling possibilities. Let us explore the leading theories.
St. Euphemia Basilica Formation
This Basilica honors St. Euphemia, who was martyred in 303 or 304 at Chalcedon. These were the days of the persecutions of Emperor Diocletian, when hundreds, if not thousands, died at the hands of the authorities. I formerly wrote about Diocletian and his connection to Nicomedia (Izmit). She first escaped death by other attempts, and church history mentions many miracles of deliverance until she was thrown to be attacked in the local arena, which most likely was located farther inland from the archeology site.
Her death and especially her testimony of faith to stand for Christ were repeated in the generations that followed her. As a young teenager, she stood in her faith despite the external pressures around her. The feast of St. Euphemia is celebrated on September 16,
the reputed date of her martyrdom in 303 or 304 at Chalcedon.
What we know about the St. Euphemia Basilica
The earliest record we have of the basilica is from the 4th century: “Then I arrived at Chalcedon, where I stopped because of the very famous shrine of Saint Euphemia, already known to me from before. On the following day, after crossing the sea, I arrived in Constantinople, giving thanks to Christ our God who deigned to bestow such favor on me, an unworthy and undeserving person.” (Egeria, written around 381-384 AD)[1]https://dn790006.ca.archive.org/0/items/ancient-christian-writers-collection/Egeria%20EN%20%28George%20E.20Gingras%2C%201970%29%20ACW%20038.pdf This reference shows us that St. Euphemia Basilica was well-known and established for some time by the late 4th-century.
Early Christian history demonstrates the priority of honoring those martyred for the sake of Christ. Many early believers refused to deny Christ’s deity and also refused to worship false images or human powers. These believers were the first to be honored with buildings, as their graves, memory, and dedication had a great impact on the faith of those who lived in Chalcedon. Many other believers desired to be buried near them or to have their bones buried near them. We see this trend in Nicomedia, Nicaea, and even in Italy, especially in Naples.
The Basilica Known from History
The Council of Chalcedon met in the Basilica of St. Euphemia in A.D. 451. This fact alone tells us that the site was far more than a simple martyrium. It was one of the most important churches in the eastern Roman world and served as the shrine that housed the tomb of St. Euphemia. Their bishops held influence and offered this location for the council.
Historical records also state that Persian forces later invaded the Asian side of Constantinople. During this period, church authorities removed the saint’s relics from Chalcedon and transferred them to the Church of the Holy Apostles in Constantinople. At a later date, they moved the relics again to the Greek Orthodox Church of St. George in Fener, where they remain today.
Possible Places of St. Euphemia Basilica
One important clue comes from local historical traditions about Chalcedon: “Among these was the Temple of Aphrodite on the shore of Haydarpaşa Bay. It is said that the Church of St. Euphemia was later built in its place. The Church of St. Euphemia retained its importance for Kadıköy until recent times. There are theories about the exact location of this first church.” (Pınar ERKAN)[2]https://gazetekadikoy.com.tr/yazarlar/pinar-erkan/antik-devirlerde-kadikoy-khalkedon
This tradition raises an interesting possibility. Temples dedicated to Aphrodite often occupied prominent and elevated locations. Famous examples include the sanctuary of Aphrodite at Corinth and other temples associated with the goddess throughout the eastern Mediterranean. If the Church of St. Euphemia replaced such a sanctuary, the church may likewise have occupied higher ground overlooking the bay rather than the waterfront itself.
The Hill Above the Harbor
Several scholars have focused on the elevated ground above Haydarpaşa Harbor. “The basilica-type church, according to sources, was located on a hill about 370 m inland from the coast, so it should be somewhere near Duatepe Street in the present-day Yeldeğirmeni neighborhood.” (Semavi Eyice)[3]https://dergipark.org.tr/tr/download/article-file/888652
This description places the church not on the shoreline but on the ridge rising behind the harbor. The area includes the heights around modern-day Yeldeğirmeni, as noted by the local writer Semavi Eyice. The Haydarpaşa hospital grounds and the slopes extending toward Selimiye could also be of interest based on the historical records. Here is my walk on the hospital grounds, where I discovered Byzantine ruins.
Guided by the tradition that the St. Euphemia Basilica stood on high ground overlooking the harbor, a few historians have focused their search on the hospital hill and surrounding elevations. Byzantine cities frequently located cemeteries beyond the settled area, often toward the eastern side of the town. Examples from places such as Antalya and ancient Side illustrate this broader Roman and Byzantine practice. In the series, I will write about some of the graves found away from the coast in Kadikoy.
Ottoman Control of the Ridge
The history of the land itself may offer another clue. In 1855, the Ottoman government granted the British Cemetery to Britain, perhaps in recognition of a past connection to Christian burials. Before that transfer, the Ottoman state controlled the property. Because the area remained under imperial authority, large-scale residential development did not occur there. Later, military planners designated portions of the district for hospitals and barracks.
During the reign of Suleiman the Magnificent, builders quarried marble and architectural stone from abandoned Byzantine monuments throughout the region. According to long-standing tradition, they also reused materials from the Church of St. Euphemia in major Ottoman construction projects.
If the basilica stood on the ridge that later came under military control, this restricted access may have protected the site from extensive civilian development while removing much of its visible structure. The cleared land later proved suitable for military facilities and, eventually, the modern hospital. Because most of this construction occurred before archaeology became a priority, builders paid little attention to preserving or documenting any buried remains.
Could the ridge beneath the present hospital complex preserve the lost site of the Basilica of St. Euphemia?
Following the Clues
No single piece of evidence identifies the church’s location with certainty, but several clues point to the elevated ground above Haydarpaşa Harbor. These include the tradition connecting the basilica to the former Temple of Aphrodite, accounts placing it approximately 370 meters inland, the presence of monasteries and cemeteries in Yeldeğirmeni, and the area’s long history of restricted access under Ottoman control.
As a result, many scholars focus on the ridge stretching from Haydarpaşa toward Yeldeğirmeni and Selimiye. Beneath this landscape may lie the foundation of one of the most significant churches of the Byzantine world.
Some argue that the modern St. Euphemia Orthodox Church offers us a clue. Builders constructed the current church in 1694 over earlier Byzantine remains. Some researchers believe that local memory preserved the sacred location through the centuries. However, archaeological evidence is scarce, and it is unclear whether this church stands directly atop the famous fifth-century basilica that hosted the council.
The Clues from Texier’s Visit in 1830s
One of the strongest pieces of evidence is actually negative evidence. Charles Texier had a remarkable eye for standing ruins. Throughout Asia Minor, he carefully sketched, measured, and described surviving monuments wherever he found them. If a substantial church had still stood on the Haydarpaşa ridge in the 1830s, he would almost certainly have recorded it.
One of the strongest clues emerges from the absence of information in the historical record of French archaeologist and explorer Charles Texier, who visited the site in the 1830s. As he traveled across Asia Minor, he carefully sketched, measured, and described all surviving monuments he encountered. If major ruins of St. Euphemia had remained, he would have mentioned them.
His silence suggests that Suleiman I (1520-1566) carried out a major operation to salvage the basilica, removing all useful pillars and marble capitals. If anything remains, only a foundation or portions of the apse would have survived. Layers of accumulated soil likely now bury what is left. Based on what endures on the ridge and in the central area used as a wooden park, it is possible that someone could still find traces of St. Euphemia there.
As this process continued, the basilica gradually disappeared from the landscape. Only scattered fragments survived above ground, while its foundations lay hidden beneath layers of soil and later development. By the time Texier arrived, the church that had once drawn pilgrims from across the Byzantine world had become an archaeological mystery, remembered in historical sources but no longer visible on the surface.
Ottoman Reuse of St. Euphemia’s Basilica?
If the Basilica of St. Euphemia stood on the Haydarpaşa ridge, transporting its marble columns and architectural stone to Ottoman building sites would have been relatively easy. Workers could have moved the materials downhill to the shoreline and then shipped them by boat to construction projects throughout Istanbul.
This possibility would prompt some researchers to examine the key sixteenth-century Ottoman monuments for reused Byzantine materials. Particular attention often falls on the Mihrimah Sultan Mosque and Şemsi Pasha Mosque in Üsküdar, as well as the Süleymaniye and Şehzade Mosques on the European side of the city. During my visits to the Mihrimah Sultan and Şemsi Pasha Mosques, I noticed features that may reflect Byzantine influence or reused materials. The columns of the Mihrimah Sultan Mosque display differing shades and markings, while the Şemsi Pasha Mosque contains visible spolia in its courtyard.
The primary evidence for this theory comes from a long-standing tradition that builders under Suleiman the Magnificent reused stone from the sanctuary of St. Euphemia in imperial construction projects. The tradition is well known, but surviving documentation remains scarce. However, no surviving inscription or archaeological record has conclusively identified a column, capital, or marble block from the basilica within any of these mosques. While the theory remains plausible, it has not yet been proven.
The Basilica of St. Euphemia may remain hidden, but the search for it continues to uncover the forgotten world of ancient Chalcedon.
Conclusion
The search for the Basilica of St. Euphemia reminds us that history often lies beneath the surface. The churches, harbors, cemeteries, and monuments of ancient Chalcedon once shaped the spiritual and civic life of the city, yet many now remain hidden beneath modern streets, military grounds, and centuries of accumulated soil.
No discovery has yet confirmed the exact location of the basilica that hosted the Council of Chalcedon in 451. Still, the historical clues, archaeological finds, and surviving traditions continue to point researchers toward the ridges above Haydarpaşa Harbor. Perhaps future excavations will finally reveal what has remained concealed for centuries.
Until then, the search itself offers a valuable reminder: understanding ancient Chalcedon requires looking beyond what is immediately visible. Some of the city’s most important stories still wait beneath the ground, ready to be rediscovered.
Like the search for St. Euphemia’s Basilica, Searching Below the Surface explores what lies beneath the surface of history, faith, and tradition. The book is available on Amazon.
References
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