Songdo International Business District (SIBD) is a new Smart City or Ubiquitous City built from scratch on 1,500 acres of reclaimed land along Incheon's waterfront, 40 miles southwest of Seoul, South Korea and connected to Incheon International Airport by a 7.4 mile reinforced concrete highway bridge, called Incheon Bridge. Along with Yeongjong and Cheongna, it is part of the Incheon Free Economic Zone. This 10-year development project is estimated to cost in excess of $40 billion, making it one of the most expensive development projects ever undertaken and it is the largest private real estate development in history. By its completion date in 2015, the district is planned to contain 80,000 apartments, 50,000,000 square feet of office space and 10,000,000 square feet of retail space. The 65-floor Northeast Asia Trade Tower became South Korea's tallest building. The plan was designed by the New York office of Kohn Pedersen Fox (KPF).