Billionaire tycoon Peter Morton's Hamptons mansion -- which he dropped $10 million to buy -- went up in flames ... and there's almost nothing left of the place.
The Hard Rock Cafe founder's castle-like crib caught fire Wednesday afternoon in East Hampton, NY -- and 7 fire departments sent trucks to fight the blaze which appeared to engulf all 10 bedrooms of the 10,000 sq. ft. beachfront spread.
Morton shared the home with his 3 adult children. No no one was home when the fire started -- though a construction company was reportedly working on the property.
Unknown what started the fire at this point, but no one was hurt ... besides Morton's wallet.
Morton bought the mansion back in 1998 -- so, it's gotta be worth more than double that $10 mil by now.