We have a set of trails locally referred to as "Tunnels", paths cut thru scrub oak by the illegals that used to live in there til they were booted several years ago. MTBs took over the area, now it's just buff singletrack thru low-overhanging branches, narrow Y branches, steep up and downs, a real workout as you have to duck as you're looking out for stuff to catch your pedals and body while negotiating the trail, you are surrounded to the point that it's like going thru a tree tunnel. This is the probably the longest of the 5 tunnels.