Istanbul, a bustling metropolis with a population of 15 million, is unique in that it spans two continents and has served as the capital of two empires. Founded by the Greeks and later the capital of the Christian Byzantine Empire, Istanbul was reborn at the heart of the Muslim Ottoman Empire following its capture by the Turks in 1453. Both empires left behind a wealth of magnificent buildings, most of which are concentrated in the old city centered on Sultanahmet. Starting your day in the subterranean depths of the Basilica Cistern, a 1,500-year-old building supported by 336 columns, is a must-see. Don't miss the twin blocks carved into snake-haired Medusas or the carp idling in the shallow waters. Right across from the cistern is the Hagia Sophia, initially a church but converted into a mosque in 1453, made a museum in 1934, and converted once again to a mosque in 2020. Look out for the superb mosaic of the Virgin and child flanked by the Byzantine emperors Constantine and Justinian above the doorway as you exit via the Vestibule of Warriors. In the afternoon, head to Tarihi Sultanahmet Köftecisi, where you can try tasty grilled meatballs dished up with a white-bean salad and spicy tomato sauce. The four courtyards and plethora of buildings and pavilions that make up the Topkapi Palace complex are a whole afternoon's entertainment. This was the nerve center of the Ottoman Empire, with several museums featuring treasures such as the Topkapi Dagger and a hair from the Prophet Mohammed. Don't miss the intriguing and beautifully-tiled Harem section of the complex, once the residential quarters of the sultan, his family, and concubines. For a nightcap, try the roof bar of the Arcadia Blue Hotel on Imran Ökten Cad, Sultanahmet, which affords spectacular views over the historic, lit-up buildings of the old city and across to Asia. On Day Two, take the T1 tram to the Laleli stop and walk north past Istanbul University's distinctive faculty of Science and Literature building (dating to 1944) to the Kalenderhane Mosque. Continue north beneath the arches of the fourth-century Aqueduct of Valens and follow it east to Vefa Bozacı’s for a traditional fermented millet drink called boza in a Victorian temperance hall style café. Walk east down steep, cobbled Fetva Yokusu and pop into Ağa Kapşs café for tea and expansive views down to the Golden Horn, Bosphorus, and distant hills of Asia. Continue downhill to the bustling Golden Horn waterfront area, popping into the exquisitely tiled Rşstem Paşa mosque before perusing excellent food shopping opportunities in
