Topkapi Palace
Home of the Ottoman sultans for nearly 400 years, Topkapi Sarayi ("Palace of the Cannon Gate") was the seraglio, the heart of the vast Ottoman Empire, ruled by the monarch who lived in Topkapi's hundreds of rooms with hundreds of concubines, children, and white and black servants.Because Topkapi is No. 1 on everyone's list of Istanbul sights, get there when it opens (usually 9 am; closed Tuesday; TL20 admission fee for adults) and go straight to the Harem (additional TL15 admission fee).
Once accessible only by guided tour, you can now wander through the Harem on your own, as you choose; but only a certain number of visitors are allowed at one time, so go there first to avoid waiting.
After wandering through the Harem you can stroll the palace's spacious grounds and four courtyards at your leisure.
Don't miss the Treasury in the 3rd courtyard, with its incredible gems, gold, and works of art.(For a bittersweet romantic scene that actually happened at Topkapi, see my Bright Sun, Strong Tea excerpt entitled "Tears at Topkapi.")
Just down the hill to the west of the palace are the Istanbul Archeological Museums, and beyond them is shady Gulhane Park, a fine place for a stroll or a soothing glass of tea.
When you're done at Topkapi, head for Ayasofya (Hagia Sophia), right next door, and the Blue Mosque, next door to Ayasofya on the Byzantine Hippodrome.