Sintra is really part of the general Lisbon area. We choose this as the location for our first night as it meant to short drive after our two flights. The town is noted for the numerous 19th-centry architecture and has a UNESCO World Heritage Site designation.
I was able to explore the city early in the morning, before anyone was up, but once the day started, we found Sintra to be congested with sightseers and it was next to impossible to find place to leave a car and explore.