A large fire in the shadow of Conisbrough Castle took around an hour to put out.
Two fire appliances were sent to Castle Hill about 10.30pm on Tuesday, where a number of large sheds behind the castle grounds were engulfed in flames.
The blaze had also spread to nearby trees and caused severe damage to the sheds.
A South Yorkshire Fire and Rescue Service spokesman said the fires had been started deliberately.
Another arson attack was reported in Doncaster town centre at around the same time.
Doncaster fire crews were called to Nether Hall Road where an outbuilding down an alleyway behind a tattoo parlour had been set alight.