Cashtal yn Ard is a well-preserved Neolithic chambered tomb dating to around 3000 BC. The tomb is located on a hill that gives great views to the east over the parish of Maughold and the Irish Sea and Barrule to the northwest. The large monument which is about 128 feet (39m) in length was originally a covered megalithic chambered cairn and has a west–east orientation. It is noted as being one of the largest and best preserved of its kind in the British Isles.
The tomb consists of a west facing open forecourt that leads to five stone chambers in the east. The forecourt measures 22 feet x 19 feet and made up of large stones of which the largest is nearly 8 feet in height. The east facing stone chambers are separated by lateral standing stone slabs. The highest of the stones forming the chambers is over 3 feet and then they reduce in size towards the east. The average width of each chamber is about 4 feet.
Excavations of the site were made in 1880's, with a more scientific investigation in the 1930's and most recently a geophysical survey in 1999. The first investigation reported the discovery of bone fragments of a young person and also pieces of two different urns. No bones were found during the later excavation, however any other human remains may have been removed during earlier disturbances. The 1930's investigation did discover flints and shards of Neolithic pottery, as well as at least 125 white sea pebbles. According to Manx National Heritage (Eiraght Ashoonagh Vannin) three separate features are thought to predate the cairn. A small stone cist, a mass of burnt stones and thirdly, an unusually large standing stone.
The site can be reached via the A15 Hibernian Road (off A2 road between Laxey and Ramsey) and then the road towards Ballaglass Glen. Pass the glen, continue around the sharp right-hand bend and up the steep narrow road until you reach a cottage on your left on a sharp left-hand bend. The public footpath to Cashtal Yn Ard is signposted on your right.