Philadelphia remains in this spot with contributing factors of greater population, density, city age and family poverty. The bright side: Tourists visiting this metro area of 5.8 million might prefer feathers over fur. They can view the city by land and water with the Ride the Ducks sightseeing tour. The vehicle goes from the streets of the historic district to splashing into the waters of the Delaware River. Don't forget your Wacky Quacker — it might come in handy for scaring away the rats!