2 Best Sights in Lisbon, Portugal

More than 2,500 years of history is on display at this archaeological treasure trove hidden beneath a bank on one of Lisbon's busiest shopping streets. The buried 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. The digs revealed homes and artifacts from the Roman, Visigoth, Islamic, medieval, and Pombaline periods, and 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 guided tours in English or Portuguese lead through underground walkways and around the foundations of ancient buildings.

The Carmelite Convent—once Lisbon's largest—was built in 1389 and all but ruined by the 1755 earthquake. The ruins are hauntingly beautiful, and the convent's sacristy houses the Museu Arqueológico do Carmo (Carmelite Archaeological Museum), a small collection of ceramic tiles, ancient coins, and other city finds. The tree-shaded square outside—accessible via a walkway from the top of the Elevador de Santa Justa—is a scenic, tree-shaded spot to dawdle over a coffee or a cocktail.