Alfama survived the 1755 earthquake — most of central Lisbon did not — and the street pattern in the old quarter is still medieval. The escadinhas, the small public stairs that ladder up from the river to the castle, are typically a meter and a half wide between four-story buildings. The sun, even at the August zenith, only briefly reaches the bottom. For two or three hours around solar noon the stairs are in the kind of cool, blue, stone-bounce shadow that older European cities used to be full of and mostly aren’t anymore.
The walk below is up. You will be climbing — Alfama goes from the Tejo at sea level to the Castelo de São Jorge at about 110 meters in roughly 700 horizontal — and the stairs are uneven. But the heat math is unambiguous. Coming down at five in the afternoon, when the sun has rotated west and the same stairs are in slanted gold, is a different walk and a fine one; it is not in this guide. A note on the trams: the 28 runs along Rua das Escolas Gerais and the rails are in full sun. Cross them quickly.