From the Parco del Collo Oppio, visitors can access the underground remains of a vast palace that the Emperor Nero built himself after the fire that devastated Rome in 64 AD. Subsequently forgoten, it served as foundations for Trajan's Baths. Impressive vaulted underground galleries give access to rooms decorated with wall paintings, which excited Renaissance artists when they first discovered them: calling them “grotesques”, a new style was born.