Build a den out of sticks on a flat spot in the woods, cover it with leaves, and you've got a pirate hideout or a meeting place for spies. There are loads of National Trust places with perfect spots for den building.
Safety is really important to us, and we've got lots of tips on how to become a '50 things' expert safely for each of the activities. We've added general advice below and links to useful websites containing more information.
Follow willow tunnels or make your very own woodland den in our natural play areas. You can also splash along muddy trails, hang onto rope swings and hunt for treehouses and bug hotels. Here's our pick of the best natural play areas at our places.