Now this is a cool site! It's an urban exploration site showcasing the places the guys who call themselves the 'Action Squad' go on. They go to many different places throughout Minneapolis, including caves and spooky abandoned hospitals. It's a fascinating and entertaining read. It may've not been updated for quite a while, but that doesn't detract too much from the experience.
Or if you want a more secure connection: https://web.archive.org/web/20170108232040/http://www.actionsquad.org/