Outer Bailey Arroyo Block, Gym and Regimental Association Club

The Outer Bailey Arroyo Block, Gym and Regimental Association Club in Carlisle was originally built as an armoury and later served as barracks. It now functions as County Council Offices, a gymnasium, and a regimental club. Constructed in 1804 by Captain Hartcup for the Board of Ordnance, the building underwent extensions around 1908 to 1912 and had a rear gymnasium and Sergeants' mess added in 1937-1938.

The structure features Flemish bond brickwork set on a chamfered red sandstone plinth, with raised quoins, a string course, and mouldings made from calciferous sandstone. The roof is covered with graduated Welsh slate and has overhanging heavily dentilled eaves, with gabled ends and brick ridge chimney stacks. The building is two storeys high and consists of seven bays, with a four-bay extension on the left that matches the original design.

The original section on the right has a central plank door framed by a painted stone architrave, and sash windows with glazing bars set in stone architraves, with the window above the entrance being blind. Each end of the building has projecting single bays that are quoined. The left extension mirrors this design but features blind windows in the projecting bay. Above the entrance is a 20th-century painted stone panel inscribed with "ARROYO," one of the battle honours of the Border Regiment, along with a wall-mounted clock. The return wall on the right has blind windows, with smaller windows without glazing bars located further right.

The interior has been extensively altered. The building was converted to barracks in 1827, and an extension from the 1840s was demolished in the early 20th century, replaced by the current extension. It was known as the Clinton Block in 1890. The Castle itself is a Scheduled Ancient Monument.