Evidence exists of human occupation of the Lacken area for thousands of years, one example of this is the Passage tomb which sits in the woods on Lacken Hill.

Lugnagun Passage tomb (National Monument Number WI00223) dates from the Neolithic (c. 4000-2500BC). 
It is part of a dispersed cluster of monuments found through the Wicklow Mountains and the adjoining parts of the Dublin Mountains. 
Neolithic Megalithic monuments are found across western Europe, mainly on the Atlantic seaboard from Spain to Ireland. Lugnagun is part of a cluster of three megalithic tombs on the ridge above Lacken.  The other two monuments at Rathnabo and Carrig (National Monument Numbers WI00180 and WI00210) flank a hill cursus (large ditch and bank – National Monument Number WI03364) and are wedge tombs.  This implies a significant ritual landscape in the Neolithic period.
The most famous passage tomb in Ireland is Newgrange.  Although called passage tombs not all contain human remains and no burials are known from Lugnagun.  Passage tombs are generally circular structures made up of a stone mound surrounded by a kerb wall and covering a passage leading to a central chamber.
The mound which would have covered Lugnagun is no longer there but a kerb of approximately 7m, is still visible.  The walling stones are mostly upstanding grey granite with some quartz veining. Two stones marking the west facing passage entrance have very large veins of quartz.  The central chamber can be seen with the remnants of a tree stump on the top of it.