# AYASOFYA BASILICA (Hagia Sophia) 8 
Designed on an unprecedented scale with a 56 m high grandiose cupola and displaying 30 million gold tiles in its interior, the Hagia Sophia is known as one of the world’s greatest architectural achievements of all time.
The exceptional building was inaugurated in 537 CE as a church by the Byzantine Emperor Justinian and remained for almost a thousand years the world's largest and most important religious monument. In the 15th century, it was converted into a mosque before being finally declared a museum (as it is today) by AtatĂĽrk in 1935.
Museum | Former Mosque World Heritage Site: since 1985
# SULTANAHMET QUARTER 7 
Best explored on foot, Istanbul's charming old town features all of Istanbul's best-rated tourist attractions in a small area.
Historic Area World Heritage Site: since 1985
# TOPKAPI PALACE 7
Situated attractively above the confluence of the Bosporus and the Golden Horn, the huge Topkapi Palace was the Imperial residence of Ottoman sultans from 1478 to 1856.
Highlights include the Imperial Hall with the throne of the sultan, the harem, where the sultan’s wives and children lived, and the panoramic view of the Marmara Sea from the gardens.
Former Palace World Heritage Site: since 1985
# Dolmabahçe Palace 6 
Sitting along the coastline of the Bosporus Strait, this monumental (285 rooms and forty-six halls) Palace, with its extravagant interior, is a unique mix of styles.
During its construction in the 19th century, fourteen tonnes of gold were used to gild the ceilings.
Palace Completed: 1856 | Open to the Public: year-round | Rooms: 285 | Style: Baroque Revival and Rococo Revival | 📵
by Mircea Ostoia / CC BY-SA 2.0
# GRAND BAZAAR 6
Dating back to the 15th century, the chaotic but wonderful Grand Bazaar is one of the world's oldest shopping malls.
Enter by one of the eleven gates into this gigantic (50 acres [0.2 km2]) colorful labyrinth of sixty-five covered streets, packed with more than 4,000 tiny shops offering carpets, gold, leatherware, cloth, and spices.
Market World Heritage Site: since 1985
# Suleyman’s Mosque 6
Built between 1550 and 1557 by the legendary Ottoman architect Sinan, this mosque is the largest and one of the most beautiful in Istanbul.
by José Luiz Bernardes Ribeiro / CC BY-SA 3.0
# Istanbul Archaeology Museums 6
Housed in a three-building complex (Archaeological Museum, Museum of the Ancient Orient, Museum of Islamic Art), this is one of the world's largest museums with over one million works on display.
Highlights include the Royal Necropolis of Sidon sarcophagi, the Alexander Sarcophagus, and the oldest peace agreement (Treaty of Kadesh).
by Giovanni Dall'Orto / CC BY-SA 2.0
# GALATA TOWER 6
Constructed in 1348, this 68 m-high tower offers a fantastic panorama of the city.
Historic Tower World Heritage Site: since 1985 | Total Height: 70 m | Observation Deck Height: 51 m | Built: 1348
# Basilica Cistern (Yerebatan Sarnıçı) 6
Constructed in the sixth century during the reign of Byzantine Emperor Justinian as a royal water reservoir, this subterranean chamber measures 138 meters (453 ft) by 64.6 meters (212 ft).
Palace-like Underground Hall Built: 532 CE
by Dpnuevo / CC BY-SA 3.0