Mountains circle Seoul on all sides with Namsan (South Mountain) springing up in the center. Although the Han River once marked the southern boundary, the city has sprawled across to the southern side with some 2 dozen bridges crossing it and one subway tunnel underneath. As Korea's capital and most populous city, Seoul represents the country's center for business, education, and modern culture. It offers many activities for everyone, including museums and palaces, parks and mountains, and amusement parks and night clubs.