This frigidarium or natatio is a circular room, which strikes you at the outset by its excellent state of preservation.  In the middle of it is hollowed out a spacious round basin of white marble, four yards and a half in diameter by about four feet in depth; it might serve to-day—­nothing is wanting but the water, says Overbeck.  An inside circular series of steps enabled the Pompeians to bathe in a sitting posture.  Four niches, prepared at the places where the angles would be if the apartment were square, contained benches where the bathers rested.  The walls were painted yellow and adorned with green branches.  The frieze and pediment were red and decorated with white bas-reliefs.  The vault, which was blue and open overhead, was in the shape of a truncated cone.  It was clear, brilliant, and gay, like the antique life itself.

Do you prefer a warm bath?  Retrace your steps and, from the apodyteros, where you left your clothing, pass into the tepidarium.  This hall, which is the richest of the bathing establishment, is paved in white mosaic with black borders, the vault richly ornamented with stucature and white paintings standing forth from a red and blue background.  These reliefs in stucco represent cupids, chimeras, dolphins, does pursued by lions, etc.  The red walls are adorned with closets, perhaps intended for the linen of the bathers, over which jutted a cornice supported by Atlases or Telamons in baked clay covered with stucco.  A pretty border frame formed of arabesques separates the cornice from the vault.  A large window at the extremity flanked by two figures in stucco lighted up the tepidarium, while subterranean conduits and a large brazier of bronze retained for it that lukewarm (tepida) temperature which gave it the peculiar name.

[Illustration:  The Tepidarium, at the Baths.]

This bronze brazier is still in existence, along with three benches of the same metal found in the same place; an inscription—­M.  Nigidius Vaccula P.S. (pecunia sua)—­designates to us the donor who punning on his own name Vaccula, had caused a little cow to be carved upon the brazier; and on the feet of the benches, the hoofs of that quiet animal.  The bottom of this precious heater formed a huge grating with bars of bronze, upon which bricks were laid; upon these bricks extended a layer of pumice-stones, and upon the pumice-stones the lighted coals.

What, then, was the use to which this handsome tepidarium was applied?  Its uses were manifold, as you will learn farther on, but, for the moment, it is to prepare you, by a gentle warmth, for the temperature of the stove that you are going to enter through a door which closed of itself by its own weight, as the shape of the hinges indicates.