i used to know one of those people who deem themselves "urban explorers" and he would guide me around the tunnels and everything. its 100000 times for complicated then you think, and its very dangerous. its no joke, make sure your prepared before you go adventuring.
im alll about abandon buildings n underground passages n that kind of shit but ya sewerz sounds like a super duper dumb idea. i mean sure its a good story to tell but you wont get much more out of it. DEFF. do ya research