Fodor's Expert Review El Zanjón de Granados

All of Buenos Aires' history is packed into this unusual house. The street it's on was once a small river—the zanjón, or gorge, of the property's name—where the first, unsuccessful attempt to found Buenos Aires took place in 1536. When the property's current owner decided to develop it, he discovered all sorts of things below: pottery and cutlery, the foundations of past constructions, and a 500-foot network of tunnels that has taken over 25 years to excavate. With the help of historians and architects, they've now been restored, and the entire site has been transformed into a private museum that's valuable urban archeology. Excellent 50-minute-long guided tours in English Monday through Friday and Sunday at 12 pm and 4 pm take you through low-lighted sections of the tunnels. Expect few visitors and plenty of atmosphere on weekdays; you can also visit next-door property Casa Mínima.