Seion Welsh Independent Chapel was built in 1870-1 to the design of Rev. Thomas Thomas of Landore. It is in the Classical style, with round-headed openings, a painted and stuccoed exterior and pitched slate roof. The chapel has a tripartite gable facade with pilasters and a major central arch breaking into the pedimented gable. The central arch contains an arched doorway with pilasters, moulded arch and keystone, below a triplet of arched windows, with a keyed roundel with date plaque in the apex.The side bays each have long arched windows with stuccoed surrounds. The side elevations have five similar windows, and the five-bay vestry adjoins the rear elevation.
The chapel interior is largely unaltered, with a three-sided gallery with cast-iron panels and moulded cornice mounted upon cast-iron columns. The pews below are curved around a semi-circular set fawr with matching cast-iron panels and a timber pulpit with canted front and stairs to either side. The organ, housed in an elliptical arched recess, dates to 1900. The plaster ceiling has a moulded border and ribs raditting from three roundels.

Source: Cadw Listed Building Record
RCAHMW Inventory Documents

K Steele, RCAHMW, 20 March 2009