Explore the grandeur of Ottoman architecture at the Blue Mosque (Sultanahmet Camii), located on Istanbul’s Old City peninsula. Opened in 1616 to rival the Byzantine-era Hagia Sophia (Aya Sofya) across the way, the six minarets punctuating the Istanbul skyline and 20,000 blue Iznik tiles decorating its interior are designed to inspire awe.

Built in 532 as the world’s largest place of worship, the Hagia Sophia (Ayasofya) shifts its identity with the times but never loses its grandeur. Converted from a church to a mosque during the Ottoman era and becoming a museum in 1935, the pink-hued Old City building is one of Istanbul’s don’t-miss attractions.

To understand the history of Turkey and the Ottoman Empire in Istanbul, explore the vast Topkapi Palace. The complex has elegant chambers, landscaped grounds, and small museum collections to admire, as well as a viewpoint over the Bosphorus and the Golden Horn. Guided tours, which can offer a more comprehensive experience of the palace, often allow you to skip the long entry lines with a guide, and usually include a visit to the palace’s harem section. Many Istanbul sightseeing tours combine Topkapi Palace with an exploration of the other top sights in Istanbu

Built in the third century, the Hippodrome was the home of now-named Istanbul’s sporting entertainment during the Byzantine era, with a wide track for chariot racing. Today, the route of the old track is covered by Sultanahmet Square (Sultanahmet Meydani), a wide open space in the center of the old city, punctuated by ancient obelisks.

Beautiful yet eerie, Basilica Cistern (Yerebatan Sarayi) isn’t your average underground well. Dating back to the Byzantine era, the huge cistern was built in the mid-500s on the former site of a basilica. More than 300 marble columns provide a grand, serene atmosphere to what was essentially subterranean water storage.

Getting lost in the Grand Bazaar is part of the experience, as every twist and turn reveals interesting Turkish goods. Built in the 15th century during the Ottoman era, the market remains an active and lively center of commerce—and today, tourism—in Istanbul. Explore the best stalls on a guided shopping tour. Many Istanbul sightseeing tours combine the Grand Bazaar with the Spice Bazaar or with other sights in Istanbul