The Qaaba in Al Haram Mosque, Mecca.
The British Museum is the most jaw-dropping of any museum I've ever been to. They're currently showing a Mecca exhibiiton, description thusly by The Browser: "Exhibition dedicated to Muslim pilgrimage is put on with Saudi help. Scholarly questions are ignored in order to accommodate Saudi and Muslim sensitivities. Is this a price worth paying, if there's a wider societal benefit?" Article here.
In the case of the U.S., criticism of Islam is often met with a muted reception from liberals and even from some atheists, because there is often a Christianist subtext. This is true, but that's exactly why atheists are the best people to speak up about the deep canyons Islam has cut in the moral landscape.