Begin your day with a visit to the Blue Mosque, built in the early 1600s, for a guided visit. Distinguished by its six iconic minarets, the mosque is a showcase of classic Ottoman architecture. Inside, 20,000 blue Iznik tiles, featuring intricate floral patterns, line the high ceiling. The interior is lit by 260 windows, once adorned with 17th-century stained glass and now replaced with replicas. One of the most popular tourist sites in the city, it is still a working mosque that is closed to visitors during prayer time. Next, visit the Hippodrome, also known as Sultanahmet Square, once the chariot, horse racing and social center of Constantinople, and the site of several historic monuments including the Obelisk of Theodosius. Learn about the history of the city with insights from expert local guides as you view the sights. Continue on to the Basilica Cistern, an astonishing underground reservoir built in the 6th century during the reign of Emperor Justinian I. Known locally as Yerebatan Sarnıcı, this vast subterranean chamber is supported by 336 marble columns, many repurposed from ancient Roman temples. Descend 38 steps into the dimly lit expanse, where soft lighting reflects off the shallow waters, creating an eerie yet mesmerizing atmosphere. Among the most famous features are the two Medusa head carvings, mysteriously placed at the bases of two columns. Once an essential water source for the city, the cistern remains one of Istanbul's most intriguing historic sites. Following lunch at a local restaurant, Break for lunch at a local restaurant, visit Hagia Sophia Grand Mosque, one of the world's greatest architectural achievements. Built in the 6th century under Emperor Justinian I, Hagia Sophia stood as the largest cathedral in the world for 900 years. Its soaring dome, immense marble pillars, and intricate mosaics tell the story of its layered history as a Byzantine church, an Ottoman mosque, a museum, and now, once again, a mosque. Gaze up at the vast dome, suspended seemingly weightless above the cavernous space, and take in the interplay of Christian and Islamic elements—glowing calligraphic medallions juxtaposed with ancient depictions of Christ and the Virgin Mary.