Isn't it? I've always been quite impressed with it. Without modern technology, the broad outline of Europe in the bottom left, Africa in the bottom right, and Asia for the whole top is in roughly the right place. Even within those (well, within Europe) most things are in the right place relative to each other. Obviously things aren't exactly the right shape or in proportion, but as a representative map rather than an exact detailing of relatively unimportant things like coastlines, it's very impressive. What's also important to remember is that Mappa Mundi is not intended for navigational purposes, but rather as a way of conceptualising the world. The top is Christ in Majesty, and Eden is just below, with various biblical locations throughout Asia.