Bay of Baku (Baku Bay) is a natural harbor of the Baku port and local yacht club, on the southern shore of the Absheron Peninsula and on the western shore of the Caspian Sea

It has an area of 50 km² and a coastline of 20 km. The bay is bordered by Sultan Cape in the east, Shikh Cape on the south-west and the islands of Qum, Dash Zira and Boyuk Zira in the south and south-east. These islands are part of the Baku Archipelago which lies mostly within the bay. These characteristics make it an ideal place for a harbor. There lies Baku Boulevard on the seashore. During severe storms with high winds, the height of the waves in the bay can reach 1–5 m.

From the 1st century AD till the 7th century, Baku bay was dry and the islands in the bay joined the land. In Ptolemy’s map Baku was described far from the sea. After the 7th century began the rising of water level of the Caspian Sea till the 9th century and since then formation of Baku bay began.[2] Severe changes happened at the end of the 8th century, when the Caspian Sea raised up to more than ten meters. A major earthquake occurred in 1306, the Sabayil Castle, built on an island in the Bay of Baku, was submerged and remained under water for several centuries. It was only in the early 18th century, when the Caspian Sea retreated, that the island resurfaced.[3] Mario Sanuto, an Italian geographer of the 14th century sadly noted that: "Water level of the Caspian Sea rises each year and most cities have flooded.", and according to words of Abd ar-Rashid al-Bakuvi, the geographer, in 1403 the Caspian Sea flooded the part of Baku and water stood near a mosque. At that time the sea was waving near foot of the Maiden Tower, which confirms a legend about a girl, who threw herself from the top of the tower. At that time Sabayil Castle, which was built on the rock in Baku bay, was totally located under water. During the next 600 years level of the sea was hesitatingly stood high till the beginning of the 20th century, when it began to sink