Personal Experience: This is the first tunnel that I have gone all the way through and man was it fun!! I think my nerves were softened because I was exploring with an experienced tunnel/urban explorer who had already gone through before. There were multiple chambers, each being quite different from the rest. I definitely recommend exploring this spot if you are into urban exploring. Make sure to wear boots with thick rubber soles. Rubber boots are a plus. The more rain we get, the more water will be inside. Any photos of me (the female) were taken by my buddy Bernie.
The tunnel entrance is shaped like a crescent moon, hence the name Half Moon: