The remains of the emperor Caracalla’s vast baths complex are among Rome’s most awe-inspiring ruins. Inaugurated in 216, the original 10-hectare site, which comprised baths, gyms, libraries, shops and gardens, was used by up to 8000 people daily.

Most of the ruins are what’s left of the central bath house. This was a huge rectangular edifice bookended by two palestre (gyms) and centred on a frigidarium (cold room), where bathers would stop after spells in the warmer tepidarium and dome-capped caldaria (hot room).

But while the customers enjoyed the luxurious facilities, below ground hundreds of slaves sweated in a 9.5km tunnel network, tending to the complex plumbing systems.

The baths remained in continuous use until 537, when the Visigoths cut off Rome's water supply. Excavations in the 16th and 17th centuries unearthed important sculptures, many of which found their way into the Farnese family's art collection.

In summer the ruins are used to stage spectacular opera and ballet performances.