Sintra is the classic destination for a daytrip from Lisbon, and I did spend a full day there, but it would be quite easy and tempting to take it slowly and dedicate 2 or more days to the area. There is definitely plenty to see to keep you occupied for quite some time. The site is a cultural landscape consisting of the centre of the town of Sintra plus several palaces in the surrounding mountains that were the favourite retreat for Portuguese royalty and nobility for many centuries. There are various types of buses available, and I chose a hop-on hop-off day pass for just 5 EUR that makes the rounds to all major sights (they arrive reasonably on time, but are often stuck in the massive traffic jams). The first stop after the station is the town centre where the National Palace is located. This medieval royal residence is quite an interesting building famous for its conic chimneys and wooden ceilings with beautiful decorations. After that, I took the bus up the winding mountain roads to Sintra's true highlight - the Pena Palace. This is really a fantastic sight, looking like a movie set or Disney attraction. As mentioned below, both Gaudi and Disney seem to have been inspired by its unique architecture and multi-coloured buildings. It is really a joy to walk around the site (still quite a long walk uphill from the bus stop) and enjoy the panoramic views over the mountains. Back in Sintra, I finished my day with a visit to the Quinta da Regaleira, a romantic palace with a large park full of features such as grottoes, lakes, and fountains that can take quite a long time to explore. Sintra is always full of tourists and, even though it is not very far from Lisbon, it is probably a better choice to stay there for a night or two to better experience a really unique site.