Day one — the monuments, early
4.2 km · 40 min
Leave by eight and walk about eight minutes to Hagia Sophia before the queues form. Topkapı Palace is next door; give it three hours, and do not skip the Harem. Come back down through Gülhane Park to Sirkeci for lunch, then see the Basilica Cistern in the afternoon, when the light outside is harsh anyway. Total walking: under an hour, spread across the day.