Domus Aurea

Nero's lost 'Golden House,' built between 64 and 68 AD after the Great Fire of Rome on a sprawling 80-hectare site that included an artificial lake (where the Colosseum now stands). The palace had revolving ceilings, gold-leaf walls, and dining rooms with frescoed grottoes that Renaissance artists — Raphael and Michelangelo among them — rediscovered by lowering themselves through holes in the ceiling, inspiring the 'grotesque' decorative style. Tours are limited and rare; book weeks ahead, and the included VR headset reconstructs the palace at its peak.