The Euromast is a tower in Rotteram constructed between 1958 and 1960, designed by H.A. Maaskant. It was specially built for the 1960 Floriade. It is a concrete building with an internal diameter of 9 meters (30 ft) and a wall thickness of 30 centimetres (1 ft). For stability it is built on a concrete block of 1,900,000 kilograms (4,190,000 lb) so that the centre of gravity is below ground. It has a "crow's nest" observation platform 96 meters (315 ft) above-ground and a restaurant. Originally 101 meters (331 ft) in height it was the tallest building in Rotterdam. It lost this position for a while, but regained it when the "Space Tower" was added to the top of the building in 1970, giving an additional 85 meters (279 ft). Euromast is a member of the World Federation of Great Towers.