A man in his 40s was hospitalised with head injuries after being assaulted in Lincoln city centre at the weekend.
The incident was reported to Lincolnshire Police just after 4.05am on Sunday, December 7.
The man was assaulted near the Stonebow in Lincoln and was taken to Lincoln County Hospital for treatment for injuries to his head.
He was later discharged and is now recovering at home.
Officers investigating believe the assault happened close to the HSBC Bank and may have involved more than one offender.
The area where the assault occurred was cordoned off for a period of time as investigations were carried out.
Anyone who witnessed the incident or has any information relating to it is asked to contact Lincolnshire Police on 101 quoting incident 76 of December 7.
Alternatively contact the independent charity Crimestoppers anonymously on 0800 555 111.