The historical centre of Baku reveals its tumultuous past, from its roots as a Silk Road port city, through its oil boom to its Soviet period. The old city is a maze of alleys, mosques, historic buildings and remnants of fortification, including the Palace of the Shirvanshahs and the Maiden Tower, now listed among UNESCO's World Heritage Sites. Much more than a historic site, the city hosts vibrant arts and cultural activities, as well as a bustling modern business sector.