Former Railway Tunnel, South Park Wood, Peebles

The former railway tunnel at South Park Wood in Peebles was opened in 1864 for the Caledonian Railway. It features horseshoe-shaped entrances on the west and east sides. The tunnel is constructed with rock-faced ashlar voussoirs and wing walls, complemented by polished ashlar courses, while the eastern entrance has droved ashlar voussoirs. The interior is lined with red stock brick.

On the west elevation, leading to the Neidpath Viaduct, there is a long sloping cutting that approaches the horseshoe arch tunnel, which has rusticated voussoirs. The coping and band courses create the appearance of a faux parapet. There is a later brick wall with a now missing central door located within the tunnel entrance. To the left, a sloped ashlar wall with deeply overhanging quoins meets the main tunnel wall, while to the right, a high wall with flat quoins also abuts the tunnel wall and steps to follow the hill's contour.

On the east elevation, facing South Wood Park, the long sloping cutting mirrors that of the west entrance. To the left, there is a brick retaining wall on the left bank of the cutting, and to the right, a natural random rock forms the retaining wall. The horseshoe ashlar arch tunnel here also features rusticated voussoirs and a droved ashlar entrance, with coping and band courses suggesting a faux parapet. Similar to the west side, there is later brick infill in the tunnel with a now missing central door. Near the tunnel entrance, remnants of a small ashlar trough can be found, along with a culvert that spans the burn to the east.

Inside, the tunnel is almost straight and lined with brick, extending from the west to the east with a slight bend towards the Peebles end. The tracks have been removed, leaving cinders and ballast from the former track bed.