Baku is the capital and largest city of Azerbaijan, as well as the largest city on the Caspian Sea and of the Caucasus region, with a population of 2,374,000. Baku is located 28 metres below sea level, which makes it the lowest lying national capital in the world and also the largest city in the world located below sea level. It is located on the southern shore of the Absheron Peninsula, alongside the Bay of Baku. At the beginning of 2009, Baku's urban population was estimated at just over two million people. Officially, about 25 percent of all inhabitants of the country live in Baku's metropolitan area. Baku is the sole metropolis in Azerbaijan.
Baku is divided into twelve administrative districts and 48 townships. Among these are the townships on the islands of the Baku Archipelago, and the town of Oil Rocks built on stilts in the Caspian Sea, 60 kilometres away from Baku. The Inner City of Baku, along with the Shirvanshah's Palace and Maiden Tower, were inscribed as a UNESCO World Heritage Site in 2000. According to the Lonely Planet's ranking, Baku is also among the world's top ten destinations for urban nightlife.