The 29-year-old man was killed on Saturday evening when a car left the road while travelling on a hillside track at Fingask Castle in Perthshire.
The victim was named locally as Steven Keddie, from Cupar in Fife.
It is understood the car crashed into a hedge next to the main drive with “considerable force”.
Mr Keddie was believed to be a friend of Emma Taylor, who married Gavin Bissett at the venue on Saturday. The couple are also thought to be from Fife.
The 16th-century castle is in the Carse of Gowrie. The Threipland family first came to Fingask Castle at the end of the 16th century and the site was bought by Andrew Threipland in 1996.
Mr Threipland said: “The police are saying nothing specific at present.
“All I know is that three young men in a car banged into the hedge at the side of the main drive here with considerable force at about 6pm and that one of them was killed.”
He added: “After the wedding ceremony, he wanted to show two friends what a wonderful place he was staying in. The car hit the hedge and rolled over. Fingask has offered the use of its facilities for a funeral to celebrate his life.”
One tribute posted on Facebook said: “There are just no words that can describe the sheer devastation that is being felt in the town today.
“Our thoughts and prayers are with all Steven’s family, friends and colleagues. Fly high, Steven Keddie, you were a true character that will be sadly missed by many.”
Amy Watson said: “Rest easy, Steven Keddie, far too many accidents happening these days – thoughts are with all friends and family.”
Diane Mower added: “Steven was so lovely, he was my hairdresser. Thoughts go out to his mum and family.”
Officers cordoned off the entrance to the castle while investigations took place.
Police Scotland’s Tayside division said: “Police Scotland can confirm that a 29-year-old man has died following a one-vehicle road traffic collision on the grounds of Fingask Castle.
“Emergency services were called to the area at about 5:40pm following reports of a collision. The driver sadly died at the scene.”