Justin Timberlake has built a giant tree house in his garden.

The 'SexyBack' singer has installed a giant den on the grounds of his Los Angeles mansion, to provide himself with a private space to hang out with his friends.

A source said: "Justin's still a kid at heard. He had the tree house built so he and his buddies could escape to drink and play cards."

The 29-year-old pop heartthrob has even banned his girlfriend Jessica Biel from entering his new pad.

The source added to National Enquirer magazine: "He even posted a sign saying 'No Girls Allowed'."

Since Justin bought his £5 million property at Mulholland Drive back in 2002, he has installed a basketball court and, more recently, a five-hole putting green so he can master his golf skills.

Justin plays off an impressive six handicap and even owns his own course, the Big Creek Golf Course near Memphis.

He also hosts an annual charity Professional Golf Association (PGA) Tour event, the Justin Timberlake Shriners Hospitals for Children Open in Las Vegas.