From the parking lot go down until you reach the river, go right (south) follows the river bank.  There are streams that get into the river on the other side.

Go across the river after the second stream. Once there, welcome to jurassic world, if you follow the stream bank for about 500m that will feel like 2km you'll get to the outside boulder.

The solar caves are 100m to the right of that boulder hidden in a dip in the ground and by much shrubbery.

The cave get flooded in the winter which make every climb full of mud once again.