The Sessions House including balustraded terrace.

This is a late 18th-century courthouse, built in the style of an Italian pavilion. It is constructed from a polychromatic combination of red rock-faced sandstone and pale yellow limestone ashlar. The building is rectangular and single-storied, with a symmetrical five-bay frontage. The end bays project and are defined by rusticated Tuscan pilasters. A deep entablature runs along the top of the building, surmounted by a parapet that has a balustrade above the central entrance bay and urn finials on either side. Each end bay features a large, round-arched sash window with an apron, scrolled keystone, hoodmould, and impost band, flanked by plain pilasters adjacent to the rusticated piers. The windows have large-pane horned sashes. The entrance bay has an arcade of three round-headed arches forming a loggia, leading to a recessed round-arched doorway with an overlight. Flanking the doorway are round-arched six-pane windows, each with a scrolled keystone, plinths, and imposts to the dividing pilasters. The intervening bays contain four-pane windows with bracketed pediment heads and inscription plaques underneath. A similar arrangement of round-arched windows and doorways in rusticated surrounds is present on the side elevation, with the southern elevation overlooking the outer prison walls. The slate roof is part-hipped and mostly hidden behind the parapet. A central glazed lantern illuminates the main hall. A corniced stack is located at the rear. A curved balustraded terrace runs along the front of the building.

Entering through the front doorway leads to a large central hall, from which symmetrical passages and doorways open. Wide six-panelled doors, some bearing painted signs, are set within grand polished wood doorcases featuring entablatures. The passages are defined by plaster arches with imposts and keystones, and have a painted dado. The hall is lit by a polygonal, panelled roof-lantern. The library contains a grey marble fireplace and bookcases that house an important legal library bequeathed by Sir Henry Mather Jackson. A central passage with steps from the hall leads to the main entrance of the courtroom. This, along with a separate rear entrance, has double swing doors with decorative ironwork. The building retains a nearly complete set of original fittings, including panelling, benches, a judge’s chair, and a gallery, all with painted labels identifying their respective uses, such as those for counsel, jury, clerk, and witnesses. The courtroom's windows alternate with blind recesses, all linked by hoodmoulds and impost bands. The wall is canted at the upper end with a gallery opposite; below the windows are portraits of judges and benefactors. Beneath the dock is a cell and passageway that once connected to Usk Prison next door.