While Sintra is home to several stunning monuments, the Pena Palace (Palácio Nacional da Pena) is widely considered the most beautiful and iconic. Perched on the highest peak of the Sintra Mountains, its vibrant yellow and red facades, Neo-Manueline architecture, and ornamental battlements create a "fairytale" silhouette that is a UNESCO World Heritage site. It was designed in the 19th century as a romantic summer residence for King Ferdinand II. However, for those who prefer an ethereal, gothic beauty, the Quinta da Regaleira with its "Initiation Wells" and mystical gardens is a strong contender. Alternatively, the Monserrate Palace is often praised as the most "accessible" and elegantly beautiful, featuring a blend of Gothic, Indian, and Moorish architecture surrounded by lush botanical gardens. In 2026, Pena Palace remains the most visited, but experts recommend booking timed entry tickets well in advance to avoid crowds and enjoy its romantic interior.