This little town 30 minutes away from Lisbon is a must go destination if you're visiting Portugal.
It feels like you're in a fairytale. It has castles, palaces and a lot of natural beauty surrounding it. If you have a chance to visit, do it and I assure you, you'll absolutely love it. I'd also advise you to read a bit about Sintra's history before visiting to ensure you don't miss anything worth being seen. I've been there 4 times and will definitely visit again.
Here are some of the pictures from my trip:
The Masonic Initiation Wells- Quinta da Regaleira 1/2
The Masonic Initiation Wells- Quinta da Regaleira 2/2
Moorish Castle from afar- built in the 8th century
Garden at Quinta da Regaleira
Quinta da Regaleira's Palace
Moorish Castle from the inside
Vale dos Lagos
Pena's Palace from afar