The Spinnaker Tower is a 170-metre landmark observation tower in Portsmouth, England. It is the centrepiece of the redevelopment of Portsmouth Harbour, which was supported by a National Lottery grant. The tower's design was chosen by Portsmouth residents from a selection of three different designs in a 1998 public poll. It has three viewing platforms one on top of the other at heights of 100 m, 105 m and 110 m. The tower was designed by local firm HGP Architects and engineering consultants Scott Wilson and built by Mowlem with steelwork by Butterley Engineering.