Man falls from Adelaide roof while trespassing

A man has been seriously injured after falling from a building in Adelaide's CBD overnight.

Police were called to Rundle Street after reports four people were on a roof top just before 1am.

Three of the four eventually climbed down a ladder to waiting police, but a fourth man tried to jump to an adjoining building and fell to the ground.

The man was taken to Royal Adelaide Hospital.

The 20-year-old from Hallet Cove sustained serious but non-life threatening injuries.

A man, 21, from Osborne, a woman, 29, from Parafield Gardens and a 20-year-old Victorian man were all cautioned for trespassing.