19th century, and contained stables and outhouses, the remains of the foundations of these buildings can be seen adjacent to the existing toilet block. The Mass Lawn area was originally a tennis court and is referred to as such by the locals. The altar on the mass lawn was constructed from the granite steps that led to the front door of the original house. The house was demolished in the 1970s following the completion of the existing hostel in 1972. President Éamon de Valera performed the opening ceremony for the new hostel. The existing main entrance is not in fact the original entrance. That entrance to the estate was some inwards and the old gateposts can still be seen. The Ice-House (bunker like building) on the lower avenue was the original "refrigerator" for the old manor house. The river would have been blocked during the winter and blocks of ice cut and placed in the pit at the end of the building. Food was then stored in layers of straw, and the building sealed up. The building was accessed during summer by way of a hatch in the roof of the building. The dolmen or cromlech is one of three that can be found in the vicinity, the others being on Tibradden Mountain and at Mount Venus. It is sometimes referred to by locals as "the druids altar" or the "druids seat". An inner ring of partially submerged boulders and an outer ring of sycamore trees surround the feature. Larch Hill International Scout and Guide Centre has two Adirondack shelters available for hire. Each shelter sleeps 8 people and they are located in the forestry above the Dolmen Field. Larch Hill is located a short distance from the Dublin Mountain Way and the Wicklow Way. River and swimming The River Glin, which is a tributary of the Owendoher River and so of the River Dodder, comes from the valley, known as Kelly's Glen, between Kilmashogue and Tibradden Mountains. During the 19th century residents of Dublin would travel to the glen to sample the waters, which were reputed to have a strong mineral content, at a spa which was situated in the upper part of the glen. A pool on the River Glin, at the lower end of the estate, was built under the directorship of Paudge O'Broin, and lasted many years, though it was out of use as of 2018.