Quinta da Regaleira Fantasy seems to be the theme of Sintra, with numerous palaces and castles dotted across this UNESCO world heritage landscape. Due to my limited time, I could only explore the Quinta da Regaleira (pictured) and the Pena National Palace. They each have large areas of parks to be explored and I would strongly recommend spending at least 3-4 hours at each site. The Quinta da Reglaeira is my personal favorite as it was super fun to explore the park with its beautiful design, underground tunnel networks and lush greenery. Totally reminiscent of Parc Güell in Barcelona.