Mynydd y Grug is officially recorded as being 355m high, however, the top has had a spoil tip added to it, taking the peak above 370m.
The Rhymney Valley Ridgeway walk skirts this hill, so the track is generally well signposted and as it is common land you can take different tracks to get better views from some of the lumps on the way up.
The views from the top in every direction are really worth the walk. You can see the English coast very clearly and all of Newport Wetlands and the power plant.
You also get good views of Caerphilly and its famous castle, as well as views North to Pen y Fan on a clear day.
This is a really good hill to walk up, it is accessible via a cobweb of footpaths and some dirt roads. You can walk from the bottom of surrounding valleys, or park on the lower part of the ridgeway and walk the last part.