Elected as one of the 7 wonders of Portugal, Mira de Aire Caves are the largest in Portugal and exploring these vast networks is certainly a unique way to see Lisbon. The Mira de Aire Caves boast 11km of extension (600m can be visited) and upon entry, you will be given a descending tour down 683 steps leading into the depths of these magnificent caves (although it looks a lot, the descent is divided up over several levels). The visit is done in groups and begins with a video with the history of the place and some interesting information. During the route, several stops are made in various viewing galleries where your guide will explain the natural development of these wondrous caves over millions of years. Kids will love looking at the colorful water features that sit at the bottom of the caves as well as the various natural rock formations that have been evolving slowly over time!