Spent a day here. Cool place with over 3000 megaliths organised in rows. Did a tour, had a picnic, went for a walk. We found information about this place to be quite misleading. There are quite a few tour operators with websites that look very official, it got quite confusing but we managed in the end.
The official visitors centre is the Maison du megaliths. This has a decent sized car park but fills very quickly as this is a popular destination. Then parking becomes a free for all on the roads etc. We arrived at 9.30 when the centre opens and all was good.
In the car park is the tourist train (independent operator, goes to the bay and then random stops along the stones. Probably useful if you don’t want to walk). Also in the car park is an unofficial guided tour that will not get you access to the stones. The staff in the centre were very helpful and spoke perfect English. We listened to the short video using the English headsets.
We booked an English spoken guided tour and access to the stones too at a paltry €9 each. The tour happened at 3pm that day so it gave us time to take a self guided walk along the excellent paths around the stone sites. The walk was 8km total and took us all the way to the end of the groups of alignments and back through some pleasant woodland.
The tour was an hour long and was informative and interesting and gave you access to the stones to walk around and touch them. This is the only way to get in to the enclosures when it is high season (April-September).
A good day out of 6500 yr old history.