Okay, my friend and I have been having this stupid argument:
What are there more of in the world; churches/cathedrals or mosques?
Please help us:) .
Er, depends how specific you are, especially with the eastern religions… not that they keep strict count…
I’ll go out on a limb and say that pretty much every nature religion wins. 
Does a mihrab count as a place of worship? I guess we’d have to count other home altars in, then. . . um. . . so never mind. Ok- real buildings, then. I’d guess churches, as Christianity in its various flavors is the most populous religion.
I’ve no figures, but my guess is that there are more churches than mosques, for the following reasons.
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According to this site http://www.zpub.com/un/pope/relig.html, there are nearly twice as many Christians as Muslims.
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Christianity is split into a lot more denominations, and each tends to have its own place of worship. Even a small US town can have six, eight or ten different churches.
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Quite apart from the system of dioceses, parishes and congregations, Christianity has a parallel network of non-congregational institutions like convents, monasteries, schools, hospitals, residences, etc, each of which will often have its own dedicated chapel. This, I think, is less true of Islam (though I am open to correction on this point).