This is our first-hand story of hiking the GR 51 from east to west. Starting in February 2009, we're making the complete journey from Menton to Marseille, but not all in one trip. We're doing it bit by bit when we can schedule the time and the necessary transportation.
Part 1: Menton, Castellar, Monti, Ste Agnes, Gorbio.
Menton - Plan du Lion
The GR 51 begins in the mountains two hours (and 700 m vertical) above Menton. Since you need to start somewhere, Menton is a good place, on the coast and on the main rail line.
The GR52 Menton to Plan du Lion page describes the trail up to the official start of the GR 51.
Start to Castellar
Castellar to Monti
The GR51 departure point to Sainte Agnes isn't very well marked. This tiny chapel is at the north end of Castellar (our photo is looking east). The faded GR red-white mark is on the narrow gatepost at the right of the chapel.
The trail starts down the cement drive at the right.
Monti to Sainte Agnes
The trail passes a small cluster of houses and then off into the wooded hills.
The mountain at the left is hiding the village of Sainte Agnes, sitting on the saddle behind this peak. In the notch down to the right we could earlier see the tall waterfall, "Cascade duBorrigo". The GR51 trail later passes a junction where a side trail goes out to the falls (closed early 2009 because of rock slides).
About an hour after leaving Monti the upward GR51 levels out at a clearing called La Virette. Stopping for a short rest, we were invaded by a group of fellow travellers: a herd of goats and attendant goatherd and his dog. Some of the goats were friendly enough to lick the salty sweat from our bare arms. The goatherd was very friendly, of course, in spite of the ferocious appearance of striding along with an ax in one hand.
This section of the GR51 ends by passing beside the "waterworks" before climbing to the junction of roads and trails at the lower edge of Saint Agnes, in front of this little chapel (602 m altitude). The GR51 from Monti and Castellar arrives from the left of this chapel.
A water source is located across the road from the chapel, with a nice grassy hillside for stretched-out resting.
Sainte Agnes to Gorbio
Behind the water source a marked trail goes up the hill to Gorbio. This is not the GR trail but a longer, steeper loop via Bausson. We've taken this trail on non-GR hiking days.
For the GR51 to Gorbio, start up the road (to the left when facing the fountain as in the above photo). The trail goes down to the left of the road (this photo). Ste Agnes village is in the upper-left corner of the photo. The trail crosses down through the pastures and then steeper down the valley to the south.
It's about an hour to Gorbio, almost all downhill. About 15 minutes down the trail, there's a 10-minute stretch up the road, then back on the trail and all downhill.
In the valley just north of Gorbio the GR51 meets with the PR that joins Ste Agnes and Gorbio via Bausson. The joined trails cross the little stone bridge for the final 5-10 minutes up to the village.