'H' Block 7, Zone J, The former Maze Prison, Halftown Road, Lisburn, BT27

H Block 7 at the former Maze Prison is a single-storey cellular unit constructed as part of Phase 3 of the prison development in approximately 1975–1976. The building comprises a central circular control area ('circle') from which four cellular wings extend in an H-shaped plan, aligned east to west. The structure is built in grey brick and concrete with a flat roof topped by a brick-enclosed water tank.

The block is set within its own fenced compound in Zone J, positioned as the central unit of three similar H Blocks arranged along the southern half of the zone. Access is controlled through a tarmac entrance yard between wings A and D, with a similar area between wings B and C. Two pairs of exercise yards to the north and south are enclosed by high metal fences of galvanised corrugated steel sheeting over welded mesh panels, topped with razor wire. The fences are fitted with regularly spaced street lights mounted on posts, and access is via tall galvanised steel and wire mesh gates topped with additional mesh, with pedestrian gates of similar construction on each side.

External elevations are regularly fenestrated with steel-framed windows, each fitted internally with reinforced concrete grilles that limit daylight. External doors are fitted with steel grille security gates. The central circle block windows have concrete grilles and are covered by later galvanised steel screens. Domed skylights light the internal corridors. External brickwork features regular expansion joints, and windows are set in simple concrete or rendered surrounds. Large insulated pipes run along the lower part of the north elevation of Wing A, supplying hot water from the mechanical and electrical plant to the block's calorifier.

The main entrance is positioned in the centre of the east elevation of the north-south circle block range. Doors are timber with observation windows, operated in conjunction with outer metal grille doors. Similar secondary doors are positioned on the western elevation of the circle, opposite the main entrance.

Two Tertiary observation towers are located centrally along the outer fence, one to the north and one to the south. These towers are square in plan with entrances on the east side. They are constructed on tubular steel frames with the lower part clad in pressed and coated pale green steel sheets on three sides, and opaque corrugated plastic sheets on the fourth side (facing away from the H Block compound). The upper observation platform projects slightly over the fence to enable wider sightlines. The observation room on each side comprises two panels of glass or Perspex, except for the outer face which continues the steel cladding of the tower below. The windows are partially darkened and mirrored using adhesive backing sheet.

Notable features distinguish this block from its sister units. The control room antechamber window and roof light are fitted with steel screens. Cell 18 marks the location of a tunnel entrance excavated during an escape attempt in 1997. The tunnel runs southward across the exercise yard, visible as a tarmac patch on the ground, with a concrete patch visible against the exterior of the cell. The escape was discovered by a patrol dog and did not succeed. B Wing exercise yard bears a Unionist slogan painted across it.

The H Block and its associated observation towers, fences, gates and gardens formed one of three original elements of the Phase 3 cellular prison. The block was occupied by different paramilitary groups; adjoining blocks occupied by the same faction were often opened into one through the locking back of dividing gates. Each cell block became an extension of the faction's neighbourhood and was decorated with murals, sometimes including street signs from areas of particular support and depicting paramilitary leaders. A six-monthly rotation of prisoner groups between cell blocks meant that artwork was painted over before reoccupation, possibly by factions with opposed views. Individual cells were also decorated with wallpaper or paintwork according to individual tastes.

The two observation towers were added in the mid-1980s to reduce staff requirements within the blocks and increase observation of the yards. The darkened windows were designed to minimise staff intimidation. The block was occupied and served its function until the prison's closure in 2000.

The building is recorded as of interest primarily due to the surviving loyalist murals and the physical remains of the 1997 escape attempt. It is not considered of special architectural or historical interest in regard to the wider legacy of the former prison.