in china, the hard as nails great wall marathon takes place on may 20.s one of the most challenging long—distance runs, drawing thousands of competitors who choose between the full length course, a half marathon, or an 8.5 kilometre fun run. starting a few hours from beijing in the heart of the mountains, the route involves steep climbs and descents, smooth flagstones to rough surfaces, and over 5000 steps. last year, the fastest speed was three hours, 30 minutes, the time to beat. back in the us, it will be man against machine from may 26—28, when the iron horse bicycle classic takes place in the colorado town of durango. the event dates back to the late i880s when two brothers raced against each other. the elder was a brakeman on a steam powered locomotive who challenged his younger brother to race the train from durango to silverton. these days, the train takes a shorter route. thousands take part, trying to beat the train before it pulls into its final destination. there are other events around the classic, including mountain biking, bmx races, dual