Newly Exposed Mosaic Structure in Lake Sapanca May Belong to a Late Antique Chapel, Researchers Say

As water levels recede in Lake Sapanca, a mosaic-floored building resurfaces, prompting renewed archaeological interest.

The falling water level of Lake Sapanca in northwestern Türkiye has revealed a mosaic-paved structure that had remained submerged for centuries. As stone foundations and sections of patterned flooring emerged from the lakebed, specialists began reassessing the site’s function and chronology. According to Dr. Görkem Işık, an art historian at Sakarya University, the remains most likely belonged to a small Late Antique religious building, possibly a chapel or a modest rural church dating between the 4th and 6th centuries CE.

Mosaic techniques hint at a Late Antique sacred function

Dr. Işık notes that the visible mosaic fragments—both in layout and technical execution—reflect artistic conventions widely used across Anatolia during the Late Antique period. Their decorative scheme, although only partially preserved, aligns with Christian liturgical spaces rather than domestic settings. Only one chamber contains mosaics, a design pattern that often marks the primary worship hall in compact ecclesiastical complexes. Adjacent rooms, now heavily eroded, would have served as auxiliary spaces.

Why is a church underwater? Shifting lake levels offer the answer

One of the central questions is why such a structure stands beneath today’s shoreline. Historical hydrological shifts, Dr. Işık explains, provide a straightforward explanation. When the building was erected, Lake Sapanca’s waterline lay considerably farther back. Over subsequent centuries, the lake gradually rose, engulfing parts of the settlement. This long-term fluctuation mirrors patterns observed at other lakeside archaeological sites in northwestern Türkiye.

Local residents report that similar water recessions occurred in the past, occasionally revealing the same foundations. Such episodic exposure confirms that lake-level changes are natural and recurrent rather than modern anomalies.

A parallel to İznik’s submerged basilica

The emergence of a lakeside Christian structure also evokes comparisons with the submerged basilica in Lake İznik, discovered a decade ago. Although smaller in scale, the Sapanca building appears to have been part of a religious landscape linked to nearby Byzantine sites. Dr. Işık highlights a probable connection with the fortified Byzantine settlement at Kurtköy, located just inland, suggesting that the chapel may have served a rural community positioned along the lake’s edge.

A rare heritage asset for a region with limited monumental remains

Unlike major centers such as İznik or Kocaeli, the Sakarya region historically hosted fewer large urban complexes. For that reason, Dr. Işık stresses the significance of protecting and studying the newly visible structure, describing it as an important cultural asset for a province with relatively scarce surviving monuments. Its preservation, he adds, will contribute not only to regional archaeology but also to heritage-based tourism.