score:4
you'll find websites telling you Pompeii is closed on May 1st, like this: http://www.pompei.biz/pompei/orario_scavi.htm However, I know for a fact that's not always the case. It was open on May 1st in 2009 and 2015. I don't really know about the Vesuvius but I found this: http://eventinapoli.com/eventi/il-primo-maggio-scalata-al-vesuvio Sorry, that's all I got.