The hajj is one of the Five Pillars of Islam; it demands that all able Muslims make pilgrimage to Mecca at least once before they die. That’s kind of a lot to ask, I imagine, especially if you find yourself without the means. But what other choice does a devotee have? Well, there’s Mecca 3D, an app that aims to deliver “a virtual world of knowledge” about Mecca and Islamic history. You can hang around the Haram—the world’s largest mosque—and interact with other worshippers, or “go back in time” to see how Muhammad and other prophets lived. And, of course, you…