I've reviewed this before and thought I should add a couple of things. Yes, this is super easy - BUT for adults and kids probably 6 and up only. It is pitch black dark without headlamps or a flashlight and I recommend both. The floor is not level anywhere and the entrance is both slippery and the rocks can move. So although easy, I wouldn't recommend it for smaller children or anyone who doesn't feel comfortable without a lot of light. You cannot see your hand without a light source.
It is also cold - around 40 degrees (we were there late June and this past September) so you really should have a jacket on and if you can, wear gloves. Gloves are great for two reasons - 1) they'll keep your hands warm 2) there are a couple of sections where you'll appreciate them because you're down on all fours basically.
Also, when I had read the reviews before we went out the first time folks talked about taking the left side versus the right side. There is only one tunnel that dead ends (yay, you can't get lost!) with basically an O in the middle of it. In other words, whether you take the right or the left you're going down the same tunnel.
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