One of the greatest Byzantine buildings in the world, Hagia Sophia is famous for its impressive size, remarkable architecture and beautiful mosaics and frescoes. The massive ochre-coloured domed structure is one of Istanbul’s most popular attractions. It was commissioned as a cathedral in the 6th century and remained the most important church in Christianity for over 900 years. In the 15th century Mehmet II conquered the city and converted it into a mosque, adding the minarets and fountains. It functioned as such for the next 481 years until the founding of the secular Turkish Republic in 1934 when it was declared a museum. The interior has elements from its time as a cathedral and then as a mosque, including incredible Byzantine mosaics, icons and marble columns, a mihrab (niche indicating the direction of Mecca), and Islamic calligraphy inscriptions on the dome from the Ottoman period.

The Blue Mosque, with its six graceful minarets and tiers of magnificent domes, is one of the most striking and immediately distinguishable buildings on the Istanbul skyline. Constructed as an Islamic rival to the Hagia Sophia in 1609, it is one of the finest examples of Ottoman architecture and is still used by hundreds of worsh ippers. The interior is splendidly decorated with thousands of blue and white Iznik tiles embellished with traditional Ottoman flower patterns, and it is this special feature that gives the mosque its name. Its design of successively descending smaller domes, soaring columns and 260 stained glass windows leaves a lasting impression of graceful accord and open space. At the back of the mosque is a Carpet and Kilim Museum exhibiting antiques from all over Turkey.

The Topkapi Sarayi, built by Mehmet the Conqueror as a Sultan's Palace, consists of a sprawling collection of buildings arranged aroun d several interconnecting courtyards. Magnificently situated on one of the seven hills of Istanbul with uninterrupted views over the Bosphorus River and the Golden Horn, it was the seat of the Ottoman Empire for almost four centuries. Home to nearly 3,000 people, it served as royal residence, harem, state administration and military barracks. One of the most popular sections is the harem, once the quarters of about 300 women who were the sultans' wives and concubines, and their children. Visitors can view the apartments, halls and terraces of the harem, and see the lavish royal bedchamber and Imperial Hall, as well as some of the greatest examples of Iznik tile work in Turkey. No expense was spared in decorating the palace and exquisitely designed rooms, intricately detailed fountains and gateways, and the splendid Treasury, housing one of the greatest collections of treasure in the world, afford insight into the opulent lifestyle of the sultans of the Ottoman Empire.