The ridge between Caerphilly and Cardiff — a 271-metre rise of common land, broadleaf woodland and open moorland that is technically not a mountain at all but is universally called one. From the top you get a long view south over Cardiff to the Bristol Channel and north back over the castle to the valleys; on clear days you can see across to the Mendip Hills in Somerset.
The Wenallt and Rhiwbina nature reserves cover the southern flank with old beech and oak; a popular short walk follows the open ridge from the Mountain Snack bar (an unpretentious roadside burger van with a cult following) along the line of an Iron Age hillfort. The Taff Trail cycle route also crosses the mountain on its way from Cardiff to the Brecon Beacons.