This wooded glen is all that remains of a forest that once covered 1000 acres. There are several waterfalls on the river, and the glen contains some mature mixed woodland of sycamore, beech, Scots pine and ash.

Lisnabreeny Former American Military Cemetery – The National Trust gifted this site to the United States forces for use in 1943. The site was used as a burial ground for 148 American servicemen who died in Northern Ireland during the Second World War, mostly in training accidents with some involved in road accidents and some dying from natural causes.  The cemetery was closed when the bodies were exhumed and reburied in England and in the USA. A memorial plaque to those who died can be found at the site.

Lisnabreeny House and the 166 acre estate in which it stood was donated to the National Trust in 1937. The estate includes a portion of the Cregagh Glen, the Lisnabreeny Rath and the site of the military cemetery.  Lisnabreeny House was briefly used as a youth hostel before it became the US army headquarters. It fell into disrepair after the war but was reconstructed by Lagan College and opened in 1991 as Belfast’s first integrated secondary school. The college occupies the site of the former house and farm buildings. The site was gited to Lagan College for the first 20 years by the National Trust.

Lisnabreeny Rath – The well preserved rath, or ring fort, is thought to have been built in the early Christian period between 500 and 1000 AD. The rath is the highest point in the Castlereagh Hills. Raths served as homesteads, providing protection for family and livestock from wild animals and warring neighbours. This fort would probably have had a simple dwelling within the protected area. The Lisnabreeny Rath gives the townland its name: in Irish ‘Lis’ means fort and ‘breeny’ means fairy, therefore ‘Lisnabreeny’ is said to mean ‘Fort of the fairy dwelling’.