The Grey Mare and Her Colts are the remains ofd a Neolithic chambered long barrow. The barrow consists of a 24m mound orientated on a south-east/north-west axis, tapering towards the north-west end. At the south-east end, it is fronted by two large sarsens, roughly 2.5m in height, which would have originally formed part of a crescent forecourt. Behind these lies a fallen capstone and the collapsed remains of the inner chamber.
The Grey Mare and Her Colts occupy a quite corner of the Dorset countryside, nicely removed from any modern encroachment. Easy enough to access, but slightly difficult to find without directions, you're not likely to encounter any other visitors.
Visually, the monument is quite striking. It's reminiscent of a poor man's West Kennet Long Barrow or Wayland's Smithy. Despite it's semi-ruinous state, it retains a lot of character and is still an impressive site in its own right. Well worth tracking down - especially if combined with a visit to the nearby Kingston Russell stone circle.