Castle Street Welsh Baptist Chapel was built in 1860/1, and though rebuilding took place c.1900, the original design of the exterior was maintained. It is in the Classical style, with two storeys, constructed from red brick with golden freestone dressings. The chapel's gable facade has three giant round arches with Doric pilasters and roll mouldings, with a pedimented gable, moulded attic roundel and rectangular plaque. It is entered via a central pair of panelled doors with fanlight over, flanked by a pair of round-headed small-paned windows, with matching windows above. The gallery level of the central bay has three round-headed windows with continuous hoodmoulds. The side elevations are roughcast with four small-pane sash windows to each floor, though many of the lower floor windows have been blocked.
Much of the original interior of the chapel was lost during renovations which turned the building into a conference and exhibition centre. The ceiling is segmentally arched with three large coloured ceiling roses. A first floor has been added at gallery level, with some original features remaining.

Source: Cadw Listed Building Record
RCAHMW Inventory Documents

K Steele, RCAHMW, 24 March 2009