The insula north of the Roman Theatre was simultaneously developed as the theatre site as a large Public Baths complex. Since the main block lies askew in its gravelled palaestra or exercise yard, it may also have started ahead of the new street grid which was laid down some time about c. AD100-110. The bath house was certainly in use by AD120.

The public baths were often altered. A second century refit turned the early cold plunge bath into a heated room, and major changes coincided with the new theatre building in the third century, when Roman Durovernum obviously was prospering. A bather would enter the apodyterium (changing area) through a western portico, paved with tesserae, after which frididaria (cold rooms) connected with a stone-paved plunge bath. The tepid rooms have not yet been excavated, but hot baths and a magnificent apsidal-ended caldarium (hot steam room) have been found with external praefurnia (stoke-holes) and drains. The caldarium may have lasted throughout the building's life, with occasional repair. By the 350's the baths had fallen out of use. Curved box-flues for removing hot gases through arched roofs lay on the collapsed pilae stacks of the underfloor heating system.

In 1987 The Canterbury Archaeological Trust excavated within St Margaret's Church during its conversion to a tourist attraction. The work followed excavations the previous year and was funded by Heritage Projects (Canterbury) Ltd.
The first area of excavation lay in the base of the church tower, where a tesselated floor had been uncovered the previous year. The floor, consisting of small white tesserae with some black in a random pattern, was largely obscured by a spread of Roman mortar and its exposure proved to be a long, painstaking task. The mosaic may date to the construction of the Public Baths in the early second century.
The second area of interest centred on a stone paved floor of the Roman cold plunge bath, also located the previous year. During that excavation it had been noticed that one of the stones bore a decorative border. This stone proved to be part of a monumental inscription in Sussex marble depicting a form of shield known as a 'pelta' surrounded by a border. The slab was reused in the floor of the plunge bath when the Baths were rebuilt in the early 4th century.
A complete photographic record of all the wall monuments and tombstones was also undertaken in advance of the building works.

An excavation carried out in 1986 revealed evidence for timber-framed buildings dating to the early Roman period which were overlain by a possible courtyard surface thought to have been associated with the bath house. The excavation also revealed that the final firing of the floor of the heated room contained demolition debris, painted plaster, box-flue tiles, and tiles from stacks which originally supported the upper floor of the heated room. This material is thought to represent deposits laid down during the robbing of material from the disused bath house for use in late Roman buildings elsewhere in the town. (5)

Frere, S. & Stow, S., Excavations along St Margaret's Street and in the Yard of the Rose Hotel (Unpublished document). SKE30129.

Pilbrow, J., 1871, Discoveries made during excavations at Canterbury in 1868 (Serial). SKE30226.

Ordnance Survey, 1874, 1st Edition Map of Canterbury 1874 (Map). SKE30106.

Blockley, P., 1988, St Margaret's Church (Article in serial). SKE30665.

Houliston, M., 1989, St Margaret's Church (Serial). SKE30666.

Blockley, K., Blockley, M., Blockley, P., Frere, S. and Stow, S., 1995, Excavations in the Marlowe Car Park and Surrounding Areas. Part 1: The Excavated Sites (Monograph). SKE29969.

<5> Canterbury Archaeological Trust, 1986, Canterbury Archaeological Trust Annual Report 1985-86 (Serial). SKE55965.