No special access issues
Coming from Albenga head to Garessio, pass Cisano sul Neva then turn left on a little bridge at the junction for Castelbianco and continue driving along the road across the Val Pennavaire. Follow the indications for Caprauna. The road ascends going through Nasino and series of hairpin turns until reach the roundabout just before the center of town of Alto, then turn right (follow the indication "santuario Madonna del Lago") and drive along the road that continues to ascend with other hairpins. After a while you'll find the street sign “santuario Madonna del Lago” on the right side of the road. Get this narrow road and drive along it until you arrive in the big parking area just in front of the sanctuary.
You can park and explore the boulder area that extends from here.
If you want to park near the boulders, remember to leave unobstructed way for locals and tourists.