Knocksink Wood NR is location in the Glencullen river valley just north of Enniskerry. Some of the valley slopes are dominated by sessile oak, while other areas are characterised by mixed woodland. Notable features of the slopes are the frequent and extensive springs and seepage areas within the woodland. The site has one of the most diverse woodland invertebrate faunas in Ireland, incorporating wet wood.
Entry to Knocksink Wood is from the Dublin Road (also known as the Monastery Road). Knocksink Wood is accessible to small vehicles and vans while coaches bringing groups have plenty of turning space and a stopping area. Smaller buses may go all the way to the car park of the Knocksink Wood Nature Reserve Education Centre, 0.5 km from the main gate (open from dawn to dusk throughout the year with the exception of Bank holiday weekends when it remains closed and is open at weekends on request).