The Spinnaker Tower is a 170 m (558 ft)-high observation tower in Portsmouth, United Kingdom. It is the centrepiece of the redevelopment of Portsmouth Harbour, which was supported by a National Lottery grant. Its shape was chosen by Portsmouth residents from a selection of concepts. The tower, designed by local firm HGP Architects and the engineering consultants Scott Wilson. It reflects Portsmouth's maritime history by being modeled after a sail. After several years of delays and cost overruns, it was opened on 18 October 2005.