Istanbul is bounded on the north and the south by the Black Sea and the Sea of Marmara. The western half of the city lies in Europe while the eastern half is situated in Asia and in between flows the Bosphorus Strait. Istanbul is a unique and unforgettable sight with its towers, palaces and the domes and minarets of over 100 mosques rising above the water. Among the city's numerous birds are the black kites and, on the Bosporus, the black cormorants. Dolphins are a frequent sight in the Bosporus and the Sea of Marmara. Most of the major attractions are derived from its huge historical status as capital of the Byzantine and Ottoman Empires. These include the Sultan Ahmed Mosque (the "Blue Mosque"), the Hagia Sophia, the Topkapi Palace, the Basilica Cistern, the Galata Tower, the Grand Bazaar, and the Spice Bazaar. Istanbul has also become an attractive shopping destination of Europe with centres like Metrocity, Akmerkez and Cevahir Mall, which is the biggest mall in Europe and seventh largest shopping centre in the world.