The tepidarium was the warm (tepidus) bathroom of the Roman baths

Thermae

In ancient Rome, thermae and balnea were facilities for bathing...

 heated by a hypocaust

Hypocaust

A hypocaust was an ancient Roman system of underfloor heating, used to heat houses with hot air. The word derives from the Ancient Greek hypo meaning "under" and caust-, meaning "burnt"...

 or underfloor heating

Underfloor heating

Underfloor heating and cooling is a form of central heating and cooling which achieves indoor climate control for thermal comfort using conduction, radiation and convection...

 system.The specialty of a tepidarium is the pleasant feeling of constant radiant heat which directly affects the human body from the walls and floor.

There is an interesting example at Pompeii

Pompeii

The city of Pompeii is a partially buried Roman town-city near modern Naples in the Italian region of Campania, in the territory of the comune of Pompei. Along with Herculaneum, Pompeii was destroyed and completely buried during a long catastrophic eruption of the volcano Mount Vesuvius spanning...

; this was covered with a semicircular barrel vault

Barrel vault

A barrel vault, also known as a tunnel vault or a wagon vault, is an architectural element formed by the extrusion of a single curve along a given distance. The curves are typically circular in shape, lending a semi-cylindrical appearance to the total design...

, decorated with relief

Relief

Relief is a sculptural technique. The term relief is from the Latin verb levo, to raise. To create a sculpture in relief is thus to give the impression that the sculpted material has been raised above the background plane...

s in stucco

Stucco

Stucco or render is a material made of an aggregate, a binder, and water. Stucco is applied wet and hardens to a very dense solid. It is used as decorative coating for walls and ceilings and as a sculptural and artistic material in architecture...

, and round the room a series of square recesses or niches divided from one another by Telamones. The tepidarium in the Roman thermae was the great central hall round which all the other halls were grouped, and which gave the key to the plans of the thermae. It was probably the hall where the bathers first assembled prior to passing through the various hot baths (Caldaria

Caldarium

right|thumb|230px|Caldarium from the Roman Baths at [[Bath, England]]. The floor has been removed to reveal the empty space where the hot air flowed through to heat the floor....

) or taking the cold bath (Frigidarium

Frigidarium

A frigidarium is a large cold pool of Roman baths. It would be entered after the Caldarium and the Tepidarium, which were used to open the pores of the skin. The cold water would close the pores. There would be a small pool of cold water or sometimes a large Swimming pool...

) The tepidarium was decorated with the richest marbles and mosaics: it received its light through clerestory

Clerestory

Clerestory is an architectural term that historically denoted an upper level of a Roman basilica or of the nave of a Romanesque or Gothic church, the walls of which rise above the rooflines of the lower aisles and are pierced with windows. In modern usage, clerestory refers to any high windows...

 windows, on the sides, the front and the rear, and would seem to have been the hall in which the finest treasures of art were placed; thus in the thermae

Baths of Caracalla

The Baths of Caracalla in Rome, Italy were Roman public baths, or thermae, built in Rome between AD 212 and 216, during the reign of the Emperor Caracalla.- History :...

 of Caracalla

Caracalla

Caracalla , was Roman emperor from 198 to 217. The eldest son of Septimius Severus, he ruled jointly with his younger brother Geta until he murdered the latter in 211...

, the Farnese Hercules

Farnese Hercules

The Farnese Hercules is an ancient sculpture, probably an enlarged copy made in the early third century AD and signed by a certain Glykon, from an original by Lysippos that would have been made in the fourth century BC...

, and the Toro Farnese, the two gladiators, the sarcophagi of green basalt now in the Vatican

Vatican City

Vatican City , or Vatican City State, in Italian officially Stato della Città del Vaticano , which translates literally as State of the City of the Vatican, is a landlocked sovereign city-state whose territory consists of a walled enclave within the city of Rome, Italy. It has an area of...

, and numerous other treasures, were found during the excavations by Paul III in 1546, and transported to the Vatican and the museum

Museum

A museum is an institution that cares for a collection of artifacts and other objects of scientific, artistic, cultural, or historical importance and makes them available for public viewing through exhibits that may be permanent or temporary. Most large museums are located in major cities...

 at Naples

Naples

Naples is a city in Southern Italy, situated on the country's west coast by the Gulf of Naples. Lying between two notable volcanic regions, Mount Vesuvius and the Phlegraean Fields, it is the capital of the region of Campania and of the province of Naples...

.