Built in the early 19th century, this staggering neoclassical palace served as the royal residence from the 1860s until the end of the monarchy (1910). You can tour private apartments and state rooms, getting an eyeful of gilded furnishings and exquisite artworks dating back five centuries, as well as the queen's chapel, home to Portugal's only El Greco painting.
It's a long uphill walk from Belém, or you can take tram 18E or several buses from downtown, including 760 from Praça do Comércio.