Heading out of Hundred house east on the A481 take the second right, pass Rhiw farm, then going uphill pass Ty'n-y-coed on your right. The bridleway is navigable right up to the top and you can park just twenty meters from the Giants grave.
As we gained height we noticed a beautiful Red Kite on our left, then another and another and one more made four, they tailed us more or less to the top. It was really very windy today but the Kites used it superbly and they effortlessly glided about searching for scraps of food.
Reaching the summit of the bridleway I could see that the barrow was in one of those saddle between two hills locations, but strangely there was another smaller bump in the ground right next to it, without the aid of Coflein I cant vouch for its age, but seeing as the big barrow is called the Giants grave we opted for the little one being called the midgets grave (please don't be offended it's just a word)
The big barrow is just that, a big barrow, no cist or kerbing, but it is big, about 4 feet tall and many feet across. From the barrow the view best appreciated is the one to the WSW towards Builth Wells.
Coflein (J.J.Hall, Trysor, 26 March 2) has this to say concerning the much smaller mound (Blaen Bedw) at SO1402954405, just north of the great Giant's Grave round barrow:
"A earthen mound, measuring 6m square x 1m high, sub-rectilinear in plan.... Its date and purpose are unknown, but it has been suggested that it may represent a prehistoric funerary monument or even a gibbet mound."
Incidentally - having watched both a tractor and (old-style) Land Rover Defender struggle up the byway - I would highly recommend leaving one's car at the entrance track to Ty'n-y-coed (just possible upon the verge) unless you are a complete loon.
As for the Giant's Grave itself... suffice to say I should have come here much sooner. But hey, there are so many upland sites to be savoured around these parts....