The Monument Boulders can be found above the monument between Garth and Trevor Rocks.
This is a pleasant, low grade bouldering venue with a large volume of problems to go at and plenty of variety. Harder traverses and eliminates can also be worked out. The landings are generally good and the aspect is very sunny. There are a few other minor bouldering crags nearby, including the Graffitti Walls, Trevor and Cefn y Feddw Quarry. The Graffitti Walls offer a range of delightful low grade problems on positive sandstone. The landings here are also nice and grassy. Trevor has a large number of problems on 3-4m high walls; there is some sections of good rock but some of the top outs are loose and should be avoided. Cefn y Feddw Quarry has around a dozen problems on decent gritty limestone.
Although well exposed to the elements the southerly aspect ensures that the rock dries quickly after rain.
If you are approaching from the west it is best to park in layby 100m beyond the monument. A diagonal path leads leftwards past the monument and onwards to the boulders.