Lisbon needs 3 days, plus a 4th for Sintra, a whole day on its own

One hill per day: Alfama, then Baixa and Chiado, then Belém

Belém is 6 km west: the Jerónimos cloister is worth the ticket

The miradouros are free, and they are what visitors remember

Tram 28: long queues at Martim Moniz; board at Campo de Ourique

Sintra is 40 min by train and needs a whole day, not an afternoon

June or September is best; the full day-by-day plan is in the guide