Byzantium. Constantinople. Istanbul. This city has held many names over the centuries as it played host to different empires and civilisations, and much of the architecture they left behind is still standing. Seeing how the buildings have evolved is fascinating, and there are plenty of mosques, churches and towers for lovers of architecture to visit.

1) Hagia Sophia

Once a church, then a mosque, now a museum, it’s difficult to comprehend just how old Hagia Sophia – also called Ayasofya – really is. Built by the orders of Emperor Justinian, the stones here hark back to the sixth century. The best mosaics are in the galleries upstairs. You can also visit the tombs to see the resting places of the early Ottoman sultans.
Sultanahmet Mh., Ayasofya Meydanı, 34122 Fatih/İstanbul 

2) Topkapi Palace

This storybook palace features on every Istanbul postcard and in every guidebook, and with good reason. Situated at the sweet spot overlooking the Bosphorus and the Golden Horn, the Topkapi was home to sultan after sultan, not to mention their many wives. You can visit the harem today and see the Topkapi treasures too. It’s a good idea to visit early or late in the day to avoid the crowds.
Cankurtaran Mh., 34122 Fatih/İstanbul (Gülhane Park, near Sultanahmet Square). 

3) The Blue Mosque

With its iconic domes and minarets, the Blue Mosque is something special. It’s unusual in that it has six minarets, and that it isn’t actually blue – unless you count the blue lights that illuminate it through the night. The building is still a functioning mosque, but you can visit outside of prayer times. Be sure to dress appropriately - arms and legs must be covered, and women must don a head covering.
Sultanahmet Mh., At Meydanı No:7, 34122 Fatih/İstanbul 

4) The Istanbul Archaeology Museum

Sadly not all the architectural gems of Istanbul are still intact. But don’t worry – you can get a sense of the grandeur by visiting the Istanbul Archaeology Museum. Or should that be museums. There are three buildings housing over one million objects from just about every civilisation in history. If time is tight, an absolute must-see is the Alexander Sarcophagus.
Cankurtaran Mh., 34122 Fatih/İstanbul 

5) Galata Tower

Galata stands head and shoulders over Beyoglu, the modern quarter of Old Istanbul. Originally built in 1348, the tower was once part of a Genoese enclave in the city. Now it’s open to tourists, and you can climb up to the top for incredible views across the city rooftops and the Bosphorus.
Bereketzade, Galata Kulesi, 34421 Beyoğlu/İstanbul. 

6) Chora Church

Like much of the finest Istanbul architecture, Chora dates back to Byzantine times. So, as you’d probably expect, the walls are lined with breathtaking mosaics. Although it may be slightly off the beaten track, the journey here is well worth it as you’ll pass some gorgeous restored Ottoman houses.
Derviş Ali Mh., Kariye Cami Sk. No:8, 34087 Fatih/İstanbul 

7) Süleymaniye Mosque

Sinan was a busy man. As Süleyman the Magnificent’s architect, he designed many mosques for Istanbul – and this one is generally ranked to be the greatest of the 42 still standing. It stretches over an extensive area, with many of the original buildings in pristine condition. The mosque is open to the public outside prayer times.
Süleymaniye Mah., Prof. Sıddık Sami Onar cad. No:1, 34116 Fatih/İstanbul  

8) Aqueduct of Valens

Emperor Valens commissioned this aqueduct in AD 378 to carry water from hill to hill, and on to the Great Palace of Byzantium. Its vast size means it’s still one of the city’s most noticeable landmarks. Around 921 metres (3021 feet) of the original structure still remain, and the Ataturk boulevard passes under its arches.
Zeyrek Mh., Haşim İşcan Gç., 34083 Fatih/İstanbul 

9) Basilica Cistern

If it gets a little too hot while you’re in Istanbul, you can always cool off underground. The Basilica Cistern was the hallmark of Emperor Justinian and completed in AD 532. The vastness of the space and the majestic columns, all 336 of them, are truly breathtaking.
Alemdar Mh., Yerebatan Cd. 1/3, 34410 Fatih/İstanbul