Spinnaker Tower in Portsmouth, England, UK with a height of 170-metre (560 ft) is the tallest accessible structure in the United Kingdom outside London. Originally named as Portsmouth Millennium Tower, it was planned for opening in year 2000 but due to delays it finally got completed in 2005 and was renamed Spinnaker Tower due to its shape. Spinnaker is a "three-cornered sail, typically bulging when full, set forward of the mainsail of a yacht when running before the wind." The shape reflects Portsmouth's maritime history.
There are triple observation decks at the top providing panoramic view of the city, its harbours and the surrounding areas up to a viewing distance of 37 kilometres (23 miles). (Wikipedia)