3 Best Sights in Baixa, Lisbon

More than 2,500 years of history are on display beneath a bank on one of Lisbon's busiest streets. A subterranean network of tunnels occupies almost a whole block in Lisbon's historic center and was unearthed in the 1990s during excavation works carried out by the bank Millennium BCP, which revealed homes and artifacts from the Roman, Visigoth, Islamic, medieval, and Pombaline periods. Much of the space was used as a major-scale Roman fish-salting factory. It was later used as a Christian burial ground, and there's even a well-preserved skeleton to be seen. Free 50-minute guided tours (book in advance) in English or Portuguese lead through the underground walkways.  

Known to locals as the Terreiro do Paço after the royal palace that once stood on this spot, Praça do Comércio (Commerce Square) is lined with 18th-century colonnaded buildings fronted by expansive esplanades. Today, trendy restaurants and cafés fill the arcades, while down by the river, the renovated waterfront promenade attracts joggers, cyclists, and sunbathers who catch rays on the steps during summer.

The equestrian statue in the center is of Dom José I, king at the time of the earthquake and subsequent rebuilding. In the northwestern corner of the square, a wall plaque recalls the day in 1908 when King Carlos and his eldest son, Luís Filipe, were assassinated as the family passed through in their carriage. (Two years later his second son, Manuel, fled the country after a republic was declared from the balcony of Lisbon's city hall, just round the corner on Largo do Município.) Throughout the year, the square hosts major events from New Year's Eve celebrations to food festivals, while kiosks—including one with an expansive terrace overlooking the river—serve potent caipirinhas and other drinks. The tourist information center and the Lisbon Story Centre museum occupy prime spots under the arcades.

The formal name for this grand public square is Praça Dom Pedro IV, but locals still call it Rossio. A gathering place since at least Roman times (it was the site of a hippodrome), it was formally laid out in the 13th century as Lisbon's main public space. Crowds socialize beside baroque fountains beneath a statue of Dom Pedro atop a towering column and amid dramatic wave-pattern cobblestones, famously reconstructed on the beach promenades of Rio de Janeiro.

On nearby Largo de São Domingos, there's a memorial to Jewish victims of a massacre in 1506, when Dominican friars egged on the mob; just three decades later centuries of more organized persecution began with the creation of the Portuguese Inquisition, which had its headquarters where the Teatro Nacional Doña Maria II now stands, on the north side of Rossio. The atmosphere today is more peaceable: locals come here to relax with a newspaper, have their boots polished by the shoe shiners, or sip a drink at one of the ginjinha bars—the one on the southern side of the square is probably Lisbon's oldest.