Yes, I've been in plenty...including mosques in Egypt, Morocco, and the great moseques of Turkey. I've also visited dozens of Buddhist shrines all over Asia. I didn't go to any of them to pray to my God...I went, observed the art, architecture and ceremony, and left. I'm not saying that a prayer offered to God there could not ascend to heaven, I'm saying that symbolically, it sends a very poor message for the head of the Catholic Church to have done so (which he gratefully did not). Since perhaps the central theme of Islam is the idea of submission to Allah, can you not see how, symbolically, the Pope's praying in a mosque under current world conditions would have looked like submission to, or at very least recognition of Allah? Praying in a place whose very walls are adorned with script proclaiming that there is no God but Allah and Muhammed is his prophet!
Instinctively you know I'm right, you just don't want to admit it.