Best 5Ks or 10Ks to run in North America?

Does anyone know of any cool 10K or 5K events? My immediate family has finally found a unique way to spend time together: training for and running in charity 5K and 10K events. We live in the Midwest of the U.S. and would love to travel around the country or the continent to participate in other races. We would love to participate in, not necessarily large events, but ones that are maybe in unique places (like the mountains, forests, big cities or other unique areas or themed events). For example: we just did one where we ran through the Milwaukee County Zoo, which we really enjoyed. Does anyone know of any cool 10K or 5K events?