The Basilica of St. Sophia, now called the Ayasofya Museum, is unquestionably one of the finest buildings of all time. Built by Constantine the Great and reconstructed by Justinian in the 6th century, its immense dome rises 55 meters above the ground and its diameter spans 31 meters. You should linger here to absorb the building's majestic serenity and to admire the fine Byzantine mosaics. (Open every day except Monday).

Facing St. Sophia stands the supremely elegant, six-minaret, imperial Sultanahmet Mosque. Built between 1609 and 1616 by the architect Mehmet, the building is more familiarly known as the Blue Mosque because its interior gleams with a magnificent panelling, of blue and white Iznik tiles. During the summer months, evening light and sound show both entertain and inform. The cascading domes and four slender minarets of Suleymaniye Mosque dominate the skyline on the Golden Horn's west bank. Considered the most beautiful of all imperial mosques in Istanbul, it was built between 1550 and 1557 by Sinan, the renowned architect of the Ottoman golden age. On the crest of a hill, the building is conspicuous by its great size, which the four minarets that rise from each corner of the courtyard emphasize. Inside, the mihrab (prayer niche) and the mimber (pulpit) are of finely carved white marble; fine stained glass windows colour the incoming streams of light.

The ancient Hippodrome, the scene of chariot races and the centre of Byzantine civic life, stood in the open space in front of the Blue Mosque, an area now called Sultanahmet. Of the monuments which once decorated it only three remain: the Obelisk of Theodosius, the bronze Serpentine Column and the Column of Constantine. Remains from the curved-end section of the Hippodrome's wall can be seen on the southwest side of these three monuments. Today the square forms the centre of Istanbul's historical, cultural and touristic activities. You should take particular note of the surrounding wooden houses, particularly the 18th-century ones on Sogukcesme Street.