One of our highlights of visiting Lisbon was taking the train out of the city to see Quinta da Regaleira, which is a huge palace with lots of property fill with gardens and cool stone structures like this. This is an "Initiation Tower" and even though it's called a tower, it's underground like a well. This is essentially a 90ft hole in the ground lined with stone, moss, and stairs. It was easily one of the coolest things I've seen in Portugal.
For this, I was happy I had my Sony 12-24mm f/4 lens. As you can imagine, this place gets photographed a lot by tourists but since it's narrow, you can't really get a photo wide enough to put everything into perspective. With the 12mm, I was about to fit almost the whole tower in the shot while still giving it a dramatic effect. Another reason why I love wide angle photography.