Temple of Mercury, Baiae
About
Despite its name, this was never a temple: it was the frigidarium of a public bath, its 21-meter concrete dome the oldest of that scale to survive from Rome. Locals also called it the Temple of the Echo, since a shout under the coffered vault rings back clearly. An oculus cut into the crown lit the cold plunge pool below, decades before Hadrian's Pantheon reused the same idea. Built in the late Republic, it stood in full working use in 117 CE.
What happened here
The furnaces are lit before dawn and the water is hot by the eighth hour, which is when the town arrives. The circuit is a habit: undress and hand your clothes to an attendant who may or may not be watching them, exercise in the courtyard, sweat in the hot room, scrape the oil and dirt off with a curved bronze strigil, then the warm pool and the cold plunge. Entry costs a coin small enough that almost nobody is priced out, and on a benefactor's birthday it is free. There is food, drink, ball games, gambling, hair-plucking, business and shouting; a writer complaining about the noise from the flat above is complaining about all of it. Men and women bathe at different hours, or in separate wings.
Sources
Nearby
Roman Maps shows the empire frozen at 11 August 117 CE, the day Trajan died — its moment of greatest territorial extent. Explore the full map →