Alfama
Climb up, see the view early, and accept getting lost on the way down.
3–4 days · May and September
Generous, if you do not underestimate the hills.
You can plan Lisbon as a flat city. You will live it as a hilly one. A ten-minute walk is sometimes a climb. Count the pause as part of the route.
Do not stack Belém on a day in the center. That half day is a monastery and a pastry shop. The city itself wants a day of its own.
Climb up, see the view early, and accept getting lost on the way down.
Dinner, and fewer postcards. You are at the top of the hill here.
Think of it apart from the center. Go before noon and linger in the pastry shop.