We took a quick day trip to Sintra, about an hour from Lisbon by train. It was beautiful with so much to see!
With just one day to explore, we focused on one attraction, but could have easily spent another day exploring other castles.
SIGHTS TO SEE:
After hiking up what felt like a mountain, we arrived at Quinta da Regaleira, our destination of choice in Sintra. It was built in 1910 and has since expanded to include a palace, chapel, extensive grounds with underground tunnels, the initiatic well, and grottoes. There is an entry fee of 6 euros for adults.
The palace itself was elaborate, but the grounds were far more impressive. 
The underground tunnel network connects the grotto to the initiatic well, the chapel, and lake. The tunnels were pitch black, so the parts with lighting were a welcome change! It felt more like a maze, and you never knew where you might end up.
After finally finding the light at the end of the tunnel, we were rewarded with the grotto!
After that, we went back into the mystery series of tunnels and popped up at one of the two initiatic wells. The exact use of these wells are a mystery, but are said to be used in some sort of initiation rites.
Other sites to see in Sintra include National Palace of Sintra, Castelo dos Mouros, and the Park and National Palace of Pena.
WHERE TO EAT:
Cafe Saudade is the cutest little cafe close to the train station. They have indoor and outdoor seating with coffee and hearty breakfast/lunch options.
TRANSPORTATION:
There is a regional train that services Sintra, departing from Rossio train station in Lisbon. Go early in the morning to maximize your time in Sintra, and also to avoid long lines to purchase train tickets. We encountered a mass of people when we arrived and barely made the train.
Once we got to Sintra, we hooved it. It was extremely hilly, so comfortable shoes are key. We checked the Uber app, and there were a few cars, but not many. Just plan on getting in your cardio! Plus, you’ll get to enjoy the hidden treasures along the walk.
Missed part 1? Read about Lisbon here. Stay tuned for part 3: The Algarve!