Evidence of Istanbul's glorious past is still seen in the ancient architecture of this bustling city. The Byzantine church Hagia Sophia is thousands of years old, and is a marvel of construction. There are ancient palaces to explore, including Topkapi, which housed rulers during the Ottoman Empire. For the traveler interested in an extensive shopping experience, the Grand Bazaar features 4,000 shops in which to browse, haggle, and perhaps buy. Super Cities: Istanbul provides a guide to Turkey's important cultural and business center.