the reserve is in area and is bisected by the afon cefni (river cefni). it was formed by glaciers during the last ice age as they eroded the soft rock of the area. it gained its current name in the 1830s and was designated as a local nature reserve in 1995, although there has been a blanket tree preservation order in place since 1971. in 2003 the reserve was granted £122,000 for major improvements including better disabled access, boardwalks and tree sculptures. it was awarded the uk mab urban wildlife award for excellence in 2004 thanks to this work. the new boardwalks mean visitors can make their way all the way north to llyn cefni, travelling parallel to the disused tracks of the anglesey central railway. red squirrels can be found in the area.