IF YOU JUDGE by the pictures, the Makkah Hilton is a nice place to stay. There’s just one catch, as the Web site notes. The five-star hotel “is exclusively sited within the Holy City which, by national and religious law, is only accessible to visitors of the Muslim Religion.” This law is something of a singularity among major religions, because it isn’t merely the Grand Mosque that is off-limits to nonbelievers, the way, for instance, a Mormon Temple is. It’s a city–a major city with hotels, supermarkets, schools and a population of 1.2 million people. (The city of Medina, population 700,000, also forbids non-Muslims.)