Sultanahmet Square occupies the ground of the Byzantine Hippodrome, between Hagia Sophia and the Blue Mosque. It functions today as a public park and is the natural starting point for a day in the old city.
Three ancient monuments stand along it, all free to see and all outdoors: the Obelisk of Theodosius, Egyptian and around 3,500 years old; the Serpent Column, brought from Delphi in the fourth century; and the Walled Obelisk. Information boards in Turkish and English stand beside each.
There are public toilets at the Hagia Sophia end, a tram stop on the north side, and shaded benches along the middle. Street vendors sell drinks and roasted chestnuts in winter.
From Hotel Yasmak Sultan the walk is around ten minutes, and the T1 tram stops here if you would rather not walk back.