This is indeed a beautiful spot. A nice little beaker/bronze age mound overlooking a stunning bay, with all of Snowdonia as a backdrop. As other people have mentioned, there is not much to see of the barrow itself; just a few large stones, but it's a great place to be - either lounging on the soft turf on a summer's day, or huddled behind the nearby stone seat when the big winter southwesterly gales are piling up the surf.
If you check out the eroded slopes just below the barrow you can pick up little bits of mesolithic flint. They're mostly just waste flakes, but it's a tangible connection to the people who were here 7,000 years ago.
The best thing to do is to park up at Porth Cwyfan (the church in the sea), and walk for a couple of miles along the coast path. This is a great little walk. The church itself is quite special, and rightly popular with artists. Further along the coast you can see the wreck of the 'Bothilde Russ' at low tide, lost in a gale in 1903. There are usually a few seals watching you from the sea, and if you're lucky there may be ravens or pairs of choughs showing off their aerobatic skills.
Overall, a great place to be. Make the effort and go there - whatever the season, you won't be disappointed.
We parked by a small bay called Porth Cwyfan right opposite a motor racing circuit and for the whole time we were there the sound of screaming motor bikes fought with the sound of breaking waves, niether won but I know which sound I prefered. Although it was a nice walk by the sea to the cairn it was by far the longest route, further back along the road was a turning and sign for a footpath and a warning not to go any further by car. As we walked down to it there was two cars and plenty of places to park, no houses, nothing to get in the way, of so damn them and drive practiaclly down to the sea. The cairn was excavated 31 years ago because of coastal erosion, but the cairn is well above the crashing waves so I'm a bit nonplussed. Only five stones are above ground and there is a dip in the centre of the cairn. This place is entirely about the place, the beaches, the rolling waves, the seabirds the mountains over to the east a whole afternoon could be spent here. If you do come don't leave your camera on show in the car as it's a ten minute hard run back to the carpark.
This is a top spot. Maybe not right up there in the list of Anglesey's 'must-see' monuments... but hey... with the kids in tow, the dunes at Aberffraw Bay looked pretty good and the cairn a bonus.
There's not much left. The rim of the cairn and a handful of decent sized kerbstones. Perched on a small spur on the west side of the bay, above the point where the River Ffraw joins the sea.With views over to Snowdon and the mountains along the coast towards the Llyn Peninsular it's a top spot.
In the CADW guide for Anglesey the cairn gets a brief mention for the Mesolithic material it covered.
When you sit at this lovely spot you can imagine the Irish king's ships turning up - he was invited over to marry the British king's beautiful sister Branwen. It looks like the ideal outdoor spot for camping and a feast.
..She was one of the three chief ladies of this island, and she was the fairest damsel in the world.
And they fixed upon Aberffraw as the place where she should become his bride. And they went thence, and towards Aberffraw the hosts proceeded; Matholwch and his host in their ships; Bendigeid Vran and his host by land, until they came to Aberffraw. And at Aberffraw they began the feast and sat down. And thus sat they. The King of the Island of the Mighty and Manawyddan the son of Llyr on one side, and Matholwch on the other side, and Branwen the daughter of Llyr beside him. And they were not within a house, but under tents. No house could ever contain Bendigeid Vran. And they began the banquet and caroused and discoursed. And when it was more pleasing to them to sleep than to carouse, they went to rest, and that night Branwen became Matholwch's bride.