I prefer watching it on screen... I'd be worried that part of the building might collapse, or water might flood in...
Have a look at Patrick Dickinson on YouTube. I love his films. He explores all sorts of abandoned tunnels etc, using fairly sophisticated camera gear and lighting. He's retired, so you don't have to be a spring chicken to do this kind of thing. He seems to know what he's doing too - I think he had employment related to underground tunnels. He's explored Sheffield's Megatron storm drain a couple of times. I think it looks incredibly spooky, but awesome.