Cashel has a varied topography with elevation rising from 10m above sea level wherethe Blair Burn crosses the public road to 586m on the summit of Binnean nan Gobhar in the northern part of the property. There are several distinct topographic features.

The Beinn Bhreac ridge, a broken craggy massif with a complex and varied relief, dominates the area. To the north of Beinn Bhreac, beyond the boundary of Cashel, Beinn Uird forms the skyline as a more rounded feature, with Ben Lomond beyond it. A prominent shoulder extending from Beinn Uird onto Cashel ground includes the rocky outcrops of Creag Thulaichean and Tom Soilleir. The upper part of the Cashel hill lies in a basin, an example of river capture.

The middle slopes are dominated by the rocky outcrops of Tom an Eagail and Creag Liath which give way to the lower slopes and relatively level south-westerly edge of the farm. The whole area is dissected by stream valleys draining towards Loch Lomond, with the most prominent and deepest being those of the Cashel Burn and Blair Burn.

To the north east of Beinn Bhreac, several mountain burns flow towards Loch Ard Forest in a north-easterly direction.