There is nothing more invigorating than waking up early in a city. Even though there are buildings, houses, and cars all around...everything is quiet. There is something peaceful about being the only one awake and running in the city. Street corners that would normally be busy are completely open. You don't have to swerve around pedestrians or worry about storefront doors swinging open. You can zip through your run in record time in the early morning. Even better-you are done with your run by the time most people are taking their first sip of coffee.
Try the Early Bird 5K for a nice run in the morning. You may want to alter this if your "early morning" equals rush hour to the rest of us.