A historical architectural monument near the Bayil settlement that is currently under water. Bayil Castle, one of the most beautiful works of the Shirvan-Absheron school of architecture, was built in the 13th century and sometimes rises to the surface of the sea and sometimes sinks into the water as the Caspian Sea rises and falls. Although the castle is referred to by various names (“Underwater City”, “Bayil Stones”, “Sabayil Castle”, “Carvansara”, “Khanegah”, “Komrukkhana”, etc.), it is more commonly known as “Bayil Castle” in scientific literature.
Bayil Castle has an elongated plan according to the shape of the island. The length of the fortress is 180 m, and the average width is 35 m. The castle walls are fortified with six semi-circular towers in the east and five in the west (as in Baku Castle). The Bayil castle was finished during a political-military era, when the Mongol campaigns shook the entire Middle East (in 1234-1235). The life of this magnificent castle, built on an island near the coast, was, however, brief. Scientists believe it sank into the sea as a result of a strong earthquake in 1306.