Sintra is one of the most impressive and attractive places to visit in all of Portugal. It is also one of the most maddeningly overcrowded. We were there in late April; boarding the local bus to drive up to the higher-situated sights, navigating the sole road that leads to those sights, or touring Pena Palace have all become rather challenging by early afternoon. I can only imagine how insane it may get in the summer.

That aside, Sintra is an exceptional mixture of nature and architecture. The inscription lists a large number of sights that comprise the overall cultural landscape. With one full day dedicated to it, most of the people would go for a few of the most famous components, which is what we did. Our first stop was the National Palace, which dates from 15th century. Inside, there is a number of attractive indoor and outdoor spaces, with some incredible azulejo tile work and elements of Mudéjar and Manueline styles. Decorated wood-panel ceilings are among the most remarkable features of the palace. One of the last rooms on the tour is the dazzling 16th-century Sala dos Brasões; the azulejos in this room are about 150 years younger and are simply phenomenal.

After the palace, we proceeded about a kilometer away from the village center to Quinta da Regaleira, which ended up as our favorite sight in Sintra. The gardens of this 17th-century villa are simply enchanting, with a number of attractive features. The palace itself is fairly compact, with only half a dozen rooms, each decorated in a distinct style. Regaleira is managed by a different company than the one managing the other major sights; its absence on the combined ticket for those sights means that some visitors skip it altogether - it does not get as crowded even closer to peak times.

Pena Palace is the most visited of all of Sintra sights, occupying top spot of one of the Sintra mountains. There was a medieval monastery at this site, partially destroyed by the earthquake of 1755. In the 19th century, king Ferdinand II built a pleasure palace here that is most distinctively colorful and combines a lot of outstanding architectural features in a very eye-catching, if somewhat contrived, way. The interior of the palace has a number of interesting rooms, among them the dining hall, the Belle Epoque Grand Hall, the Arabic Room with three-dimensional wall and ceiling paintings, and the kitchen. Unfortunately, this is one place where interior photography is not allowed. There was a half-an-hour-long line to enter the palace – entry tickets are rechecked there, for whatever reason – and we almost skipped going in, but decided to persevere for once, and that turned out to be a rewarding choice. 

The Moorish Castle dates from at least the 9th century - it is one of the oldest monuments in the Sintra landscape and obviously a sight not at all like the palaces. An old church on the grounds hosts a fairly interesting interpretative center on the history of the Sintra region. There is a path running from the castle to the village center below, providing an alternative to the buses for connecting the upper and lower sights; I suspect only the most athletic visitors will enjoy using it on the way up, but if you plan to finish with Pena and the castle here, you certainly save yourself the aforementioned aggravation with buses by walking down the path (buy one-way ticket on your ride up).

We also spent some time in the heart of the village, which is quite commercialized yet full of agreeable visual details.

As our experience shows, you can see key points of interest and get a good overall impression of Sintra in a single day, while travelling from/to Lisbon on the local train (which runs roughly every half hour from whichever terminal in Lisbon you choose – most people will go through Rossio). And we also fit in a pretty good hour-long sit-down lunch, as well as lost over 40 minutes in midday while waiting on the bus for the driver shift change to take place. However, the number of attractions in Sintra can easily support a two-day stay. In that case, you would still start with the National Palace on the first morning and then proceed to Regaleira; afterwards, you could include additional sights, such as Monserrate Palace, which is located a bit further afield. Then, start the second day at Pena, which will have smaller crowds in the morning; and spend some time in the Pena Park, reputedly also quite delightful, which we had to cut from our itinerary. Afterwards, see the castle and you may even have time remaining for one or two lesser sights.