Best Way to Get To / Spend Time in Sintra

[jeana]

I have been reading the posts and they have been immensely helpful.
I will be traveling to Lisbon on the Grand Princess for just a day (a Sunday, 7am-4pm) and want to visit Sintra.

I believe the ship docks outside Rossio at a tram station called Alcantara Mar. I can get to Rossio or other stations from Alacantara Mar, but wondering if there is a direct route to Sintra.

Also, since my time there will be limited, can anyone suggest one palace/castle that is best to spend time visiting? I understand the bus will make a circular route and I want to enjoy visiting at one of the stops.

Many thanks,
and happy travels,
Jeana