Habost souterrain, also known as Càrnan a Ghrodhair or An Taigh fo Thalamh is a souterrain or stone-lined underground passage, which lies beneath a WW2 look-out post next to a cemetery on the Habost machair, in the district of Ness, Isle of Lewis. Comunn Eachdraidh Nis are currently excavating the inside of the look-out post and souterrain, as part of a larger project celebrating the Year of History, Heritage and Archaeology.

It was discovered in the early 1940s during the construction of the look-out post, which still remains in situ over the souterrain. Information contained in a letter written by Mr R A Stuart to the Royal Commission in 1968 describes the discovery of a flagged floor by the workmen who were digging the foundations for the look-out post. One of the flagstones (possibly a roof lintel) was removed and a stone-lined passage was revealed beneath it, leading down at an angle for 20 to 30ft, before opening out into a beehive cell about 6 or 7ft high. This could be seen on the ground surface by a slight depression. An apparent unevenly smoothed ball of orthocite was found in the souterrain in 1942 and is now in Glasgow Art Galleries and Museum, although there is no knowledge of this artefact in the museum.

The souterrain remained open until the late 1950s, when it slowly began to fill with rubbish, including redundant metal wreaths from the nearby cemetery. One Ordnance Survey reviser visited the site in 1956 and described the passage as being 10 to 12ft long, and the chamber 12ft diameter, partly blocked by stones and rubbish. By 1969 the entrance was almost fully blocked with rubbish and soil.

Several people in Ness remember exploring the souterrain as children, when it was last accessible in the 1950s. Part of this project will record their memories of visiting the site.