A man suffered a fractured skull after he was attacked by a man he'd recently made friends with at the Forest Recreation Ground.
It was reported he befriended a man whilst sat on a bench and walked along talking.
He was then violently assaulted by the man and was rushed to hospital after the attack in Noel Street, near the Forest Recreation Ground, at 1am on Monday (February 22).
A weapon was used in the attack, police said.
The man is currently under observation by doctors at Queen's Medical Centre and his injuries aren't thought to be life threatening.
Detective Sergeant Simon Carter said: "The man remains in hospital after he sustained a fractured skill.
"He is under observation by doctors and his injuries are not deemed to be life-threatening.
"Officers were swiftly on the scene following the report from East Midlands Ambulance Service and located him.
"It was reported he spoke to the man whilst he sat on a bench at Forest Rec, on the Mansfield Road side first.
"The offender then walked with him on to Noel Street, before he was assaulted by an unknown weapon.
"My team has been working to establish who was behind the attack and we are determined to bring them to justice.
"We have increased police presence in the area to provide reassurance and to address any concerns the public have."
He added: "Nottinghamshire Police takes all reports involving weapons extremely seriously.
"We work really hard to take as many weapons as possible off our streets and to educate people on the dangers of carrying them.
“I would urge anyone who saw this incident to come forward.
"Detectives continue to investigate local CCTV footage and are asking for anyone who saw anyone suspicious in the area to come forward to help with our inquiries."
Anyone with information is asked to call the force on 101, quoting incident 19 of February 22 .
Alternatively Crimestoppers can be contacted anonymously on 0800 555 111.
