From Amsterdam and Barcelona to Boston and New York City: the marathon is a runners supreme test. These are the 42 most interesting, beautiful, and unique ones along with all the practical information a runner needs to join in: when theyre run, how to register, how to train for the events, the level of difficulty of each one; and which courses are hottest, coldest, and most spectacular. Some exotic choices include the Kilimanjaro Marathon, for those who can face the altitude; the Great Wall Marathon around Beijing; and the Flying Tortoise on the Galapagos Islands.