The Portal Tomb Mount Venus (also known as Woodtown Dolmen) is located near the southwestern section of the “Western Parkway” of the M50 motorway, close to “Mount Venus Road” in Tallaght, South Dublin, Ireland, in rugged terrain on the eastern slope of Mount Venus Hills. It is situated 200 meters east of the Owerdoher River, which flows into the River Dodder near Rathfarnham, with the mountains of “Sliabh na Craobhai” to the south, “Sliabh Thigh Brodain” to the southeast, and “Sliabh Chill Mochiog” to the east. Portal Tombs are megalithic structures found in the British Isles, characterized by two equally tall, upright stones with a doorstone in between, forming the front of a chamber covered, in part, by a massive capstone.

Although partially collapsed and overgrown with bracken and shrubs, the Portal Tomb was once an especially large megalithic structure. At the entrance, where only the broken part of the once approximately 4.5 meters high portal stone now stands, the massive capstone, measuring approximately 6.0 meters in length, 3.0 meters in width, and 1.9 meters in thickness, supports, reaching a height of about 6.4 meters. The other end of the capstone is now lying on the ground. The second, nearly 4.5 meters long portal stone is lying beside it.

William Borlase (1695–1772) believed that this was a variation of the Portal Tomb, which he called an “earth-fast dolmen” due to the contact of the capstone with the ground at the back end (another example would be Aideen’s Grave on Howth in the same County). However, this term is not recognized by modern archaeology. While it is possible that the capstone at the rear side was never lifted, other monuments show that such achievements were well within the capabilities of Neolithic builders. It is likely that the site has been deprived of some stones over time.