The direct passes across it from Herat (the Baba and the Ardewan) wind amongst masses of disintegrating sandstone for some miles on each side of the dividing watershed, but farther west the rounded knolls of the rain-washed downs may be crossed almost at any point without difficulty.
Where the rock projects it more usually appears in low crags and knolls, from which long trails of grey or purple debris descend till they are lost among the grass.
These various rocky masses, presenting great differences in their powers of resisting decay, have yielded unequally to disintegration: the harder portions project in rocky knolls, crags and cliffs, while the softer parts have been worn down into more flowing outlines.
The summit is a plateau from which three rocky knolls rise up, that on the west being the lowest, that on the south-east the highest.
The position of Colonus itself is marked by two bare knolls of lightcoloured earth, which caused the poet in the same chorus tc apply the epithet "white" (ap'yii-ra) to that place.