I love the pacific northwest and in the parks in seattle you can find amazing western red cedars, laurel, rhodendron and various other trees to play in, once you get into the woods though the trees mostly grow straight up and with few low lying limbs. Fallen trees, rocks, and creeks provide ample opportunity for movement but I still envy regions with trees that regular produce low lying limbs. In california and much of the american south there are amazing oak trees that produce the most spectacular movement possibilities.
Andrew Juntenen from the sacramento parkour scene just produced a great video featuring some of the oak trees around sacramento.
Jereme Sanders in Texas has produced some similarly great tree movement in his videos.
Producing a california tree runner video is high on my personal list of ambitions too.
So if your somewhere with good oak trees go find some and enjoy playing on them if not next time you visit an area with low sprawling oaks make sure to take advantage and for now find what you can in your own local environment.