Tokyo Marathon
Tokyo Marathon 2008 is going to be held on February, 17th. 150,000 people applied and only 30,000 get to run. Those lucky 30000 are decided by drawing lot. As with other major marathons in the world(maybe Boston is an exception), there are many foreign residents seats pre-allocated so I think most of(or all) who applied with foreign address gets to run on 17th.
Being the most populous city in the world, there's no shortage of people cheering you from roadside. Air is relatively clean. Long 7 hour time limits. Running water-front, Ginza, historical Asakusa area, high rise business center and imperial palace won't tire you. Oh yes, there are many shops along the way when you need a rest or food. So, do come by next year.
