From an ancient mosque to a brand-new entertainment center, these are the buildings you have to see in Turkey’s largest city, Istanbul. Plus, learn the awe-inspiring history behind these buildings and their architects.

　　Earlier versions of the descriptions of these buildings first appeared in 1001 Buildings You Must See Before You Die, edited by Mark Irving (2016). Writers’ names appear in parentheses.

　　Hagia Sophia (or the Church of the Holy Wisdom) is a former cathedral that was converted into a mosque in 1435 and then into a museum in 1935 and again into a mosque in 2020. It was originally built as part of the newly founded Constantinople for the Roman emperor Constantine in 326. It was rebuilt by Justinian in 537. Its plan was drawn up by two men who were better known as scientists than architects—Anthemius of Tralles, an expert in projective geometry, and his colleague Isidore of Miletus, a teacher of stereometry and physics.

　　It is perhaps the designers’ theoretical approach that resulted in the project, which challenged structural norms. The vast central dome spans 107 feet (32.6 meters) and is raised more than 164 feet (50 meters) above the nave, which is in turn compressed by a series of interlocking domes, semidomes, and apsidal spaces. Beneath it, 40 clerestory windows allow shafts of suffused light to cut into the structure so that the dome appears to float. The dome was the first to be built using the pendentive—an architectural device that resolves the meeting of the curve of the dome and the right angle of the wall below. This redistributed the weight of the dome, though there have been a few collapses over the years.

　　From the exterior, the building is striking above all for the evident complexity of massed geometric forms, although there is no clear facade to the design. Sixteenth-century minarets, added when the church was converted to a mosque, give the building an intelligible frame. Once the largest cathedral in the world, Hagia Sophia is still regarded as a sacred space by many Christians and Muslims. (Fabrizio Nevola)

　　Crowning the Third Hill in Istanbul is the vast complex of domes and minarets that is the Süleymaniye, the finest of the city’s mosques. Completed in 1557, it dominates the skyline, just as its founder, Süleyman the Magnificent, dominates Ottoman history. It stands as a monument not only to the greatest of the sultans but also to Mimar Sinan, his chief architect. Born a Christian, Sinan was drafted into the elite Corps of Janissaries and forcibly converted to Islam. He was the chief architect of the Ottoman Empire, responsible for no fewer than 80 mosques, 34 palaces, and countless schools, hospitals, tombs, and public baths. When Süleyman decided to raise his own mosque in 1550, he inevitably turned to Sinan.

　　The basic plan, with a huge 90-foot- (27-meter-) wide central dome flanked by two semidomes, follows that of Hagia Sophia, built a thousand years earlier. However, in Hagia Sophia the central area beneath the dome is separated from the aisles by colonnades on each side. In the Süleymaniye, Sinan made his supporting piers so tall and spaced them so far apart that he created the impression of a single vast continuum. Decoration is restrained: only the stained-glass windows and the Iznik tiles—turquoise, coral red, and deep blue—provide color. With four minarets that are the highest in Turkey, the Süleymaniye mosque is the crowning glory of Islamic Istanbul. (John Julius Norwich)

　　Baghdad Kiosk at Topkapı PalaceThe Topkapı Sarayı (Topkapı Palace) is a vast rambling complex built after the Ottoman sultan Mehmed II conquered Constantinople (now Istanbul) in 1453. It differs from many royal palaces in its seeming lack of symmetrical order. This holds particularly true for some of the smaller structures within the palace, where among gardens and wooded landscape lie tentlike pavilions and ”kiosks.” The kiosks are domed structures on columns with open sides and were places to eat, drink, read poetry, listen to music, and enjoy the remarkable views of the Bosporus.

　　Many were built to commemorate military victories. For example, Sultan Murad IV was responsible for building the Revan Kiosk and Baghdad Kiosk on the belvedere platform adjacent to the tulip gardens. They were built to commemorate the conquests of Revan and Baghdad respectively.

　　The octagonal Baghdad Kiosk lies in the Fourth Court of the palace and was designed by a master of Ottoman architecture, Mimar Kasim, who was responsible for rebuilding various parts of the palace. Behind the slender marble columns of the entrance hall is a low building with windows reaching almost to the ground, ensuring comprehensive views. The walls of the kiosk are richly decorated with Iznik tiles reaching to the base of the dome. The woodwork on the doors and window frames is decorated with inlaid mother-of-pearl, ivory, and tortoiseshell. Inside, velvet-covered divans line the walls to provide comfortable and lavish seating. (Fabrizio Nevola)

　　Dolmabahçe Palace On the European shore of the Bosporus in Istanbul stands one of the most lavish palaces in the world. It was built for the Ottoman sultan Abdülmecid I, who wanted a building to serve as the imperial family quarters and accommodate the court administration as well as provide enormous state rooms where visiting rulers and ambassadors could be entertained. The imperial architect, Garabet Amira Balyan, delivered a building that performed all of these functions with a grandeur and a scale that is almost overwhelming.

　　The style Balyan chose was an ornate Neo-Baroque. Double-height porticoes and rich carving produce an effect that combines grandeur with ornate and expensive decoration. But the long facades and the array of accommodation wings are nothing compared with the interiors. Here again, vast scale is combined with rich and intricate ornament. Grandest of all the many rooms is the ballroom, with its 118-foot- (36-meter-) high dome and its rows of columns and arches. On a similar scale is the staircase hall, its double-horseshoe-shaped stairs famous for their crystal balusters. The palace also boasts seemingly endless series of reception halls, richly gilded private rooms, and alabaster-lined bathrooms.

　　When Turkey became a republic in the 20th century, the palace, which had been completed in 1855, became the Istanbul residence of the country’s leader, Mustafa Kemal Atatürk. In 1938 he died in the palace and lay in state there. In Turkey the building is now seen as a monument to him as much as to the extravagant sultan who created it. (Philip Wilkinson)

　　Borusan Parkorman Expedition CenterThe Fatih Forest in the Istanbul suburb of Maslak has always been a place where the metropolis’s citizens could gain respite from the extreme temperatures in the summer months. The master plan for this area, conceived by GAD Architects, proposed to establish a differentiated set of venues at Parkorman Park to be used for sports activities and recreation in the daytime and concerts and other events at night. Borusan Automotive was one of the companies to rent space in the park, building Borusan Expedition Center. The center was intended to serve as a space for educational and training purposes for staff and visitors and to highlight the company’s innovative style.

　　The design of the building interacts with the existing landscape. The sloping site is dominated by century-old pine trees, which by law cannot be cut down. Thus, the building was designed as a “landscraper,” half dug into the undulating topology. During the building process, a part of the building had to be buried deep into the ground in order not to harm the roots of the pines. The impression of a building growing out of the slope is emphasized by a huge metal ramp that makes both levels accessible by car or bike.

　　The architects used durable and cost-efficient materials for the modular structure of the building, which was completed in 2001. The huge window panels help to camouflage the 3,000-square-foot (284-square-meter) volume during the day but turn the illuminated café and showroom into one of the main attractions of the park at night. The closed walls of the Expedition Center are made of steel with a metal cladding that will rust over time, making the aging of the material and the building visible. Gradually, the Borusan Expedition Center will become a part of the landscape. (Florian Heilmeyer)