The famous half of Istanbul sits within a kilometre of itself in Sultanahmet; the more interesting half is the water, the bazaars and the neighbourhoods you take a ferry to reach.
Topkapı Palace
The Ottoman court's palace above Seraglio Point, run by the National Palaces administration. Closed Tuesdays, ticket office 09:00 to 17:00, and the combined ticket covering the palace, Hagia Irene and the Harem was 2,750 TL for foreign visitors. Pay for the Harem; it is the part worth the queue.
Hagia Sophia
The sixth-century Byzantine church that became a mosque, then a museum, and has been a working mosque again since 2020. The arrangements for foreign visitors have changed repeatedly since then, including a separate ticketed upper-gallery route, so check what applies on the day rather than trusting an old blog post.
A Şehir Hatları ferry on the Bosphorus
The municipal ferry company runs both commuter crossings and a long Bosphorus tour from Eminönü up to Anadolu Kavağı. The commuter routes cost an ordinary transit fare and show you most of the same shoreline, which makes the cheapest thing in Istanbul also one of the best.
The Grand Bazaar
Around four thousand shops under vaulted roofs at Beyazıt, run by the traders' association and closed on Sundays and public holidays. Go for the jewellers' lanes and the old han courtyards off the main axes rather than the carpet pitches near the gates.
Galata Tower
The 14th-century Genoese tower in Beyoğlu, now a ministry-run museum at Büyükhendek Caddesi 2, open 08:30 to 23:00. The late closing is the point: go after dark and you skip the daytime queue and get the city lit up instead.