Police say the site had been the scene of an alleged assault and confirmed officers have made an arrest in connection with the incident.
The doorway which was cordoned off had blood on a step, outside the former Co-op building on Printing Office Steet.
South Yorkshire Police Insp Lynne Lancaster said: “We had a report of a male being assaulted in the early hours of the morning. A suspect is currently in custody.”
The injured man was taken to Doncaster Royal Infirmary where he was receiving treatment for head injuries. There was no suggestion any weapon was involved in the incident.