Never been to that one personally but I've done a fair bit of location work around abandoned institutions in the UK and there's definitely something about those old basement spaces that feels different to the rest of the building. Hard to explain rationally.
What specifically happened down there? Was it the usual cold spots and noise stuff or something more unusual? I ask because with poltergeist-type activity the basement is often where it concentrates, especially in buildings that had a lot of human suffering attached to them. Whether thats environmental or something else is the bit I can never quite make up my mind about.
Anyone else been to this place? Would love to hear more accounts before jumping to conclusions about what's actually going on there.