The Karoo is sharply divided into the Great Karoo and the Little Karoo by the Swartberg Mountain Range, which runs east-west, parallel to the southern coastline, but is separated from the sea by another east-west range called the Outeniqua -Langeberg Mountains.
The only sharp and definite boundary of the Great Karoo is formed by the most inland ranges of Cape Fold Mountains to the south and south-west.