Yes, Sintra is absolutely worth seeing and is widely considered the best day trip from Lisbon in 2026. This UNESCO World Heritage site is a "fairytale" landscape of mist-covered hills, ancient cork forests, and eccentric palaces that feel like they were pulled from a storybook. The primary highlights include the vibrant, yellow-and-red Pena Palace, the mysterious and occult-themed Quinta da Regaleira (with its famous "Initiation Well"), and the ruins of the Moorish Castle that offer panoramic views of the Atlantic. However, because of its immense popularity, it is only "worth it" if you plan carefully. In 2026, the town faces significant "overtourism," and the narrow, winding roads are often gridlocked. To have a positive experience, you must book timed-entry tickets online for Pena Palace weeks in advance and arrive at the Sintra train station as early as 8:30 AM. Taking the 434 tourist bus or a local "tuk-tuk" is much better than trying to drive a rental car. For those who dislike crowds, visiting the lesser-known Monserrate Palace or the humble Convento dos Capuchos offers the same mystical Sintra atmosphere with a fraction of the tourists.