Tempio di Diana

The great domed hall known as the Temple of Diana in Baia was not a temple, but the largest and latest of the gulf's monumental Roman bath rotundas. Built against the wall of an ancient volcanic crater, it dates probably to the third century AD.

Why it matters

The park identifies the building as part of a thermal complex that used Baia's mineral springs. Its place in the sequence of domed halls follows the Augustan Terme di Mercurio and the Hadrianic rotunda known as the Temple of Venus. The name of Diana came from a marble relief depicting a procession of animals, found in the area and associated with the goddess.

What to notice

The hall forms a vast cylinder beneath a hemispherical roof. It leans against the crater slope, which served as a support for the complex. Urban growth and the railway now separate it from the visible remains of the Parco delle Terme di Baia. The relationship between the hall and the wider bath complex remains uncertain because systematic excavation around the building has not been carried out.

Context and history

The park's scholars date the masonry to around the third century AD. Some have proposed a connection with the palace that Alexander Severus built at Baia for his mother, Julia Mamaea, but this remains a hypothesis rather than an established attribution. The building later served in the medieval practice of curative bathing before its abandonment. Antiquarians mistook its great dome for a temple, and that name remains attached to the monument and the square around it.