Your quest is to find both of the Two Towers traditional caches ; Shelob's Lair GC8EE9 and Flotsam and Jetsam GC8EE3 gathering partial coordinates from each which will lead you to the final cache Helm's Deep GC8EDC which is a 30mm ammo cache.
Here we find Frodo, Sam and Smeagol approaching the Pass of Cirith Ungol on the western side in the Mountains of Shadow. Hopefully you wont smell the horrible stench coming from Shelob's lair, nor will you run into her or her minions.
You can mountain bike this multi cache, but you will have to leave your bike at least once to walk up to 200 feet as the crow flies, so you may want to just hike it.
Recommended parking: N 41 37.036 / W 87 48.101
*10/21/2007 - Thanks go out to Shemyawalker who made a second trip back to Shelob's Lair to straighten out some confusion caused by the reappearance of the original container which had gone missing a couple years ago. Thank You Shemyawalker!