Wild Walkers offers some great and fun tours of Lisbon. I cannot recommend this experience enough. Even if its "free" and you can tip what you like at the end, the knowledge of the city, its history, and the fun and friendly way its presented is of the highest quality! This is the second time (August 2019, August 2020) that we took the Old City (around the Castle) Tour with Hugo. We told him that we had already taken the tour once and he added in new stories we did not hear the first time around! During Covid regulations, the tours are now limited to 10 people so please RESERVE in advance. We travel the world and this company is by far the most authentic, less commercially oriented I have ever found. If you want a real local's view of Lisbon, highest quality information on the history and culture, this tour is perfect. The other people on the tour were also very friendly, fun and nice - its great for people traveling solo or with friends or families (kids probably 7 and up who do not mind walking - I do not know what the actual age recommendation is). We would go on at least one tour on every visit to this city!