The nature reserve consists of a hill with the same name and the surrounding area.
From the top of the hill, there is a beautiful view over the sea and the island Balgö.
For a long time, Gamla Varberg and its surroundings was a grazed outfield.
On the heathland at Gamla Varberg, there are species like devils-bit scabious, wild thyme, Pedicularis sylvatica, and marsh gentian.
Inside the nature reserve, there are birds like the northern lapwing, common redshank, and Eurasian oystercatcher.