Caller Crag is clearly visible from the B6341 Alnwick-Rothbury road, on the NW facing hillside. It is split into 3 main parts, the lower boulders, which are passed on the way up to the main crag, and two sections a couple of hundred metres apart further up the hill.
Fell Sandstone Carboniferous, Dinantian
The rock on the main crag in particular is a poorly consolidated Fell Sandstone. A feature of the rock is that it is covered in what appear to be drying cracks - patterns of interlocking polygons 20 - 50 cms across. These never materialise into real cracks, with the result that were the rock of better quality there would be many fine, hard routes and problems here. The lower boulders are made of better stuff, but are disappointingly vegetated.
The 3 routes described are quite good, but were the rock a little harder there would be a wealth of hard, bold wall routes.
Most of the bouldering is on the outcrops you pass on the way up to the crag, at the end of the wood on the left. These problems are described in the Bouldering Guide. There is a traverse at the LH end of the main crag and potential elsewhere, but the rock is too soft for anything of real quality.
Other interesting stuff:
A large panel of Bronze Age rock carvings was discovered above the crags. Most of the carvings are cup marks, numbering about 50 in total, but there is also a duct and groove and a cup with a single ring around it.
(taken from the Keys to the Past Website hosted by Durham County Council)