How many days should you spend in Lisbon?
Three or four days works well for many first-time visitors, especially if you treat Sintra or Cascais as separate decisions. Give Lisbon real time for food, neighbourhoods and the river, but do not let every day become a queue for the next viewpoint.
Answer
Lisbon is not a city to rush straight through, but it is also easy to overfill. The best first visit separates city days from side trips. One day for the centre and river, one for neighbourhood wandering and food, one for Belém or museums, and one for Sintra or the coast can make sense. The catch is the hills: distances that look small can feel larger by late afternoon, especially in heat or crowds. Lisbon rewards slower wandering more than landmark collecting. If you only have a week in Portugal, resist giving the capital everything. Leave room for Porto, the Douro, the Algarve or wherever the rest of the route is actually pointing.