The Pena Palace is a Romanticist castle in São Pedro de Penaferrim, in the municipality of Sintra, on the Portuguese Riviera. The castle stands on the top of a hill in the Sintra Mountains above the town of Sintra, and on a clear day it can be easily seen from Lisbon and much of its metropolitan area.
Check out this tour:
https://www.viator.com/tours/Lisbon/Sintra-Regaleira-and-Pena-Palace-tickets-included-from-Lisbon/d538-43728P20?pid=P00012552&uid=U00356192&mcid=58086
Or this half day tour:
https://www.viator.com/tours/Lisbon/Pena-Palace-in-the-Aternoon-Skip-the-Line-Guided-Tour/d538-62432P3?pid=P00012552&uid=U00356192&mcid=58086