The North South Line section of Dhoby Ghaut (Code: N1) was the first to open, doing so on 12 December 1987. It was formerly named The Istana, where the president's palace is located. The platforms were built under the former Stamford canal. It became an interchange station with the opening of the North East Line on 20 June 2003 (Code: H5), while the North South Line part of the station underwent upgrading which was completed in 2006. It to date remains the only interchange station serving the North South and North East Lines.