Rorate Caeli

One day an atheist walked into a church

" I had been but a few moments in the church when I was suddenly seized with an unutterable agitation of mind. I raised my eyes, the building had disappeared from before me ; one single chapel had, so to speak, gathered and concentrated all the light ; and in the midst of this radiance I saw standing on the altar lofty, clothed with splendours, full of majesty and of sweetness, the Virgin Mary, just as she is represented on my medal. An irresistible force drew me towards her; the Virgin made me a sign with her hand that I should kneel down ; and then she seemed to say, That will do! She spoke not a word, but I understood all." 
Marie-Alphonse Ratisbonne

Read the full story of  his miraculous conversion  here: https://archive.org/stream/theconversionofm00bussuoft/theconversionofm00bussuoft_djvu.txt

Moral: this is but one example of the countless miracles that can happen when you hang around Catholic Churches. So dear atheists and hypocrites be on your guard!