Galata was a Genoese colony for two hundred years before the Ottomans took the city in 1453, and the bones of that earlier place — the medieval walls in patches, the tower at the top, the steep streets between — are still the spine of the neighbourhood.
Three kilometres, evening light, the long way up. Start at the T1 Karaköy stop and head west along Bankalar Caddesi — the old banking street, late 19th-century stone, the Imperial Ottoman Bank building now SALT Galata when it's open. Two hundred metres in, the Camondo Stairs spill out of a side cut: a pair of curves the banking family built in the 1860s, possibly the most photographed steps in Istanbul.
Climb them. Wind through the streets above to Serdar-ı Ekrem — the lane that circles Galata Tower at hilltop level. Espresso here before the queue. Time the tower entry for the half-hour before sunset; the 360-degree balcony at golden hour is what you came for.
End at Galata Mevlevihanesi above Tünel — the 1491 dervish lodge, the quietest stop on this walk. Şişhane metro is two minutes' walk; the F2 funicular drops you back to Karaköy if you want to repeat any of it.