On a lovely Sunday in October we went to Belem. It is a great place, vibrant, and full of history. We walked along the promenade to Torre de Belem. On a Sunday many attractions are free including the Torre de Belem. There was a queue but it didn't take long to get inside. The structure is very photogenic both inside and out and it is great way to spend an hour. Traffic lights inside mean only a certain amount of people are in any one area at a given time, so it is never overpacked.