Sintra is a smallish town 28 km northwest Lisbon, Portugal. It is heavily touristed but still charming, and is a very good place to visit if you don't speak Portuguese. It is approximately 45 minutes from Lisbon by train from the Rossio Station. It is a UNESCO World Heritage Site.
Sintra boasts three main tourist attractions: the Castelo dos Mouros (Moorish Castle), the Palacio Nacional (National Palace) and the Palacio da Pena. The Castelo dos Mouros is the ruins of an eighth century castle constructed at the top of a mountain by Portugal's Muslim rulers. The ruins are fascinating, including the outer walls, which are still intact, along with towers used for defense. The walls afford a magnificent view of the surrounding country. Inside, there are the remains of a chapel and several disembodied doorways.
The bus ride to reach the castle (I don't recommend hiking to the top of the mountain unless you have a lot of time and determination) was an interesting experience. The bus was, of course, extremely full, so I was standing, hanging with one hand onto a leather strap hung from the ceiling. In typical Portuguese fashion, the bus went ridiculously fast around the constant switchbacks along the road. (Portugal, incidentally, has the highest auto accident rate in Western Europe.) Thus, the passengers are continuously thrown into one another. Perhaps halfway through the trip, the bus stopped. We waited. I began to worry. Turns out, cars were parked on both sides of the road, and the clearance was just too narrow to go through. So, eight of the brawnier male passengers exited the bus, lifted the car, and carried it several feet to allow the bus to pass!
The Palacio Nacional is a national monument, a building (or conglomeration of buildings) added onto continuously over hundreds of years. It is covered in azulejos (blue glazed tiles with intricate designs) and features Gothic, Mudejar, and Renaissance architecture. Its most obvious feature from the outside are the two very large, white, conical chimneys that sit above the kitchen.
The Palacio da Pena is a fantastic castle built in 1839 for a German prince. It is considered a the best example of Portuguese Romantic architecture, painted in yellow, blue, and pink and looks like something out of a Disney movie. It is fully furnished, unlike most castles, as the royalty who inhabited it were chased out by a mob in 1910 with none of their personal belongings.
The rest of the city, both the historical and modern sections, is charming and deserves some exploration. It features several very good restaurants and it shouldn't be too hard to find a cheap hotel room if you bring a decent travel guide. There are several other historical features worth checking out as well.