Chico is immune from liability for injuries plaintiff suffered when a limb of a 130-year-old oak tree fell on her while she was jogging in a city park.  While the park as a whole was improved property–with roads, running paths and picnic areas, the tree was unimproved.  Under Gov. Code 831.2, a governmental entity is immune from liability for an injury caused by a natural condition of any unimproved public property.  The natural growth of indigenous trees in natural habitats is a natural condition, even if the city took some steps, such as pruning the tree.  What we have here is combination of a human activity and natural forces which, over time produced “a condition similar to those which occur in nature.”  Since the tree grew from an unimproved area of the park, the immunity applies, even though the limbs and roots extended into improved areas of the park.