Sintra is the site of an old Royal Palace and located around an hour's train ride West of Lisbon. I'd hit Lisbon pretty well on a previous visit so wanted to explore a little further out and being a UNESCO site Sintra looked perfect!
The train to Sintra runs out of Rossio station. A little tip here is that Rossio Metro station isn't the nearest station to the Rossio Railway station; Restauradores is.
Tickets are easy to purchase costing only 5 euros and the line ends at Sintra. Another tip is that there are two stations with "Sintra" in their name. Don't get off at the first one, wait until the last one.
Avoiding the hawkers offering expensive tours of the city I walked the mile walk from the station round to the city, it's very scenic with this, the Camara Municipal, welcoming you!
That's the National Palace of Sintra.
When you've walked around to it there's a bus stop just in front from which you can catch a local bus to the other sites in the town. 5 euros will get you a single hop-on-hop-off round trip covering the castle and palace and a second route in a smaller bus will get you to some of the other buildings for a couple of euros. It's much cheaper than the other buses.