Frankfurt (Located in the center of Germany) 8.1 million visitor

    The 2,000-year-old city has much to offer: skyscrapers, the Main River, a famous opera house, thriving theater district, zoo, pedestrian shopping street, parks, scores of bars and dance clubs, and more than 50 museum. Many people travel through Frankfurt for business, as it's a major transportation hub and an industrial and financial metropolis. Of course we know that business travelers hate to have any fun on the road , but it's worth lingering in Frankfurt if you can.