Brighton's Royal Pavilion Gardens has been added to Historic England's most 'at risk' register.
It is now said to be threatened and in urgent need of repairs.
22 sites in total have been added to the register this year.
These include the No 2 Battery in Gosport, Hampshire and Northumberland protected wreck site in Kent.
However 32 sites have been removed from the register.
These include the Argos Hill Windmill in East Sussex, Newbury Battlefield in Berkshire and St John the Baptist Church on the Isle of Wight.
Over the past year, Historic England has offered £612,000 in grants to help some of the region's best loved and most important historic sites.
The Heritage at Risk Register 2017 reveals that in the South East, 89 Grade I and II buildings, 214 scheduled monuments, 94 places of worship, 25 registered parks and gardens and 64 conservation areas are at risk of neglect, decay or inappropriate change.