The Siambr, entered from the Cwrt, is a large circular space at the heart of the building and is defined by the dramatic funnel form in the main roof. Below the funnel, the Siambr has a tiered floor. The timber desks are bespoke items of furniture, hand crafted from Welsh oak and discreetly integrating appropriate technical equipment. The Siambr floor is timber and the walls at the lower level of the drum of the Siambr are clad in acoustic panels that facilitate the Siambr’s acoustic performance.
On the level above, accessed directly from the Neuadd, the public viewing gallery is situated around the outer edges of the Siambr, separated from the Siambr itself, for security reasons, by the lower glazed portion of the funnel. This gallery seats 128 people, including press and there are 12 spaces for visitors who use wheelchairs. Some of the seating is in an elevated tier to maintain views into the Siambr. This space has fabric acoustic panel walls, a carpeted floor and low level lighting.
On either side of the Siambr two internal courtyards are formed by two deep slots cut into the plinth, which provide daylight for the sequence of committee rooms and offices on the ground floor. These courtyards also add to the transparency of the building by allowing views into the private spaces from the public levels above.