It took me a second. The black spot above the red/white thing was a trick. It looks like two entrances. The one next to the 90 degree turn the bottom of the tree makes. That is the cave. The other, if real, is down and to the left of the middle of the photograph. The top of it has a metal roof thing. That is the drainage opening.

Was I right about the entrance?

Also, what kind of gear do you use? Or do you just use your phone?

bridge.com not found: abort, retry, fail?

I cannot. On an entirely unrelated note, the exit looks pristine.