Seven play zones such as mini forts are hidden amongst the trees of the Old Arboretum; built with recycled wood felled as part of the arboretum's tree management programme.
The Gloucestershire arboretum is managed by the Forestry Commission, which has a national policy to encourage more children to play outdoors.
Simon Toomer, arboretum director, said: "When people visit somewhere historic they instinctively think they should keep to the paths.
"We want to encourage visitors to get off the paths and explore among our trees. We have developed areas buried within the tree collection for children to play and learn in."