Spokesperson Colonel Thembeka Mbhele said four men had tied the man's wrists and flung him off the cliff, in what the police regard as attempted murder.
Further details of why he was thrown into the depths of the gorge were not immediately known, but according to Blue Security, somebody who lives in the area heard cries for help on Tuesday night and reported it.
ER24 paramedics, the police, the security company, a volunteer rescue team called RescueTech, and the Gillets Fire Services set up a rescue base at the Bridle Road entrance to the Krantzkop Nature Reserve.
That spot is a favourite with photographers because of its sweeping views, and is close to a picnic site.
The paramedics scrambled down the gorge to where the man lay, and saw that he was in a serious condition.
ER24 spokesperson Russel Meiring said they had started giving him advanced life support, while the RescueTech team secured their anchor ropes and started abseiling down to him with a rescue stretcher.
The man was brought up to the top in the rescue stretcher as quickly as possible and taken to the RK Khan Provincial Hospital for further treatment.
Police were investigating.