Being a peninsula bounded by bodies of water to north, east and south (the Golden Horn, Bosphorus and the Sea of Marmara, respectively) and by the old city walls to west, this part of the city is essentially what used to be called Constantinople, as the rest of what is today Istanbul was part of independent cities, towns, villages, fields or even complete wilderness later absorbed by the city. This process is still going on as Istanbul grows with increasing speed.
Istanbul, or Byzantium as it was called then, was first settled by Greek colonists from Megara in Greek mainland in 667 BC. They founded their city at Seraglio Point (Sarayburnu) which is now occupied by Topkapı Palace. However, recent discoveries in a metro construction site in Yenikapı (on the southern coast of the peninsula) dates the very first date of Istanbul’s settlement back to about 8000 years ago, which makes the city one of the oldest still-inhabited spots of the world. This peninsula was declared a World Heritage Site by UNESCO in 1985. Sultanahmet, walking distance to the all historical sights of Istanbul named old city.
Hagia Sophia (Aya Sofya), Sultanahmet Square (by tram: Sultanahmet), +90 212 522-17-50. Tu-Su 09:00-18:00. Dating from the sixth century, it was originally a basilica constructed for the Eastern Roman Emperor Justinian I. A masterwork of Roman engineering, the huge 30 m diameter dome covers what was for over 1000 years the largest enclosed space in the world. The church was looted by the fourth Crusaders in 1204, and became a mosque in the 15th century when The Ottomans conquered the city. It was converted into a museum in 1935. Don’t miss the excellent mosaics, including those in the gallery, reached by a stone ramp to the left of the entrance. As of April, 2016, the entrance fee is 40 TL (credit cards & Turkish currency accepted), with no student deductions. The Museum Pass is also accepted. You can also hire a guide at the entrance of the museum. Note: as of Dec 2011, the museum consists of a few poster boards of pictures and a little information. As of May 2019, construction work is being carried out. Hagia Sophia is still open, but there is scaffolding (mostly inside) on about one third of the visitable area.
Sultanahmet Camii, aka Blue Mosque
At Meydan Sokak 17, Sultanahmet (by tram: Sultanahmet), +90 212 518-13-19. May-Oct 09:00-21:00, Nov-Apr: 09:00-21:00. With its six minarets and sweeping architecture the Sultanahmet or ‘Blue’ Mosque impresses from the outside. Unlike Haghia Sophia, this is still a working mosque, entry is through the courtyard on the SW side which is back side of mosque. No shorts or bare shoulders (shawls are provided) and you will need to remove your footwear (bags are provided that you can place your shoes in).
Entrance is free, but donations are welcome upon exit. The mosque is closed during ritual prayer but mosque volunteers provide you with a free presentation about the Mosque and also about Islam during that period. The venue for this event is the Mosque’s conference hall. It is the building with “Free Event” sign that will be on your left while you are approaching the Mosque from Hagia Sophia. There is no entrance fee, and there is even free refreshments. Women need to wear head scarves, which can be bought in nearby shops for 5-15TL or borrowed at the mosque for free. Everyone needs to cover their legs (no shorts or short skirts).