Arachnophobia, the fear of spiders, and agoraphobia. You can explain agoraphobia as the fear of helplessness. I get scared in wide open spaces, big rooms, corridors or other areas which are either hard to oversee or leave you unprotected, with no possibility to hide. I only get scared when I'm alone though. I fear that, if something was about to happen, there'd be no one to help me in that situation.