I will be in chicago next Saturday and Sunday, which unfortunatly is in the middle of my training for a marathon. I need a place where I can get a good 18 mile run in. I am staying at the Hyatt Regency Chicago. Are there any runners out there who may have a suggestion of where to run and how I can measure my distance in Chicago? I know that along the lake is an option, but how can I measure it out, is anything already pre-measured and marked?