Mausoleum of Augustus

The circular tomb (28 BC) of Rome's first emperor and the entire Julio-Claudian dynasty — Augustus, Tiberius, Caligula, Claudius, Nero (his ashes brought from outside the walls), plus their wives and heirs. The original structure was 87 metres in diameter, topped with cypress trees, statues, and a colossal bronze Augustus, and was the largest tomb in the ancient world. After centuries of decay and use as everything from a fortress to a concert hall, it reopened in 2021 after a major restoration; book through the official site.