There are speleologist and “urban explorer” websites, people who explore NYC subway stations that were shut down decades ago as well as abandoned mental institutions, prisons, ghost towns such as Centralia, PA, etc. It’s interesting, but dangerous and in most cases constitute trespassing.
They often document their exploration with photographs and put them up on web sites dedicated to such activities.
I have to admit I don find many of them interesting!
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The vast network of underground chambers and tunnels at Fort Warden in the northeast corner of the Olympic peninsula is an interesting place to explore.
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