Sultanahmet (Old City)
Plan to devote an entire morning to the historical structures within the walled confines of Sultanahmet, Istanbul's Old City. Start by descending the 52 stone steps to the Basilica Cistern, a subterranean, cathedral-size space commissioned some 1,500 years ago by Byzantine emperor Justinian. Raised walkways lined by 336 columns—many of which were salvaged from ruined temples and bear ornate carvings (look for two heads of Medusa in the Cistern's further reaches)—stretch over limpid pools of water. The Ottomans used the cistern to supply Topkapi Palace, but more recently it featured in the 1963 James Bond classic To Russia with Love. Emperor Justinian also commissioned the nearby Hagia Sophia, whose wide, flat dome was hailed as an engineering marvel when it was built in the sixth century. After admiring the 30 million gold tiles cladding its exterior, climb to the mezzanine to view mosaics of the Byzantine emperors, Christ, and Mary. Next door is the Blue Mosque, so named for the blue Iznik tilework that adorns some of its interior spaces. With its six minarets and dramatically cascading domes, this working mosque, commissioned by Ottoman Sultan Ahmed 1 (source of the Turkish name for Istanbul's Old City, Sultanahmet), is one of Istanbul's most photographed sites. Note that it is closed from 30 minutes before to 45 minutes after prayer times and on Friday mornings.