Whilst it is only the 27th tallest building in London today, when it opened in 1966 it was the tallest, and one of the first skyscrapers in London.
The building famously stood empty for many years, as developer Harry Hyams wanted to rent it all to a single tenant, and was thought of by many as a symbol of the greed of property developers. It was eventually let, and has since been sold to another property company, Targetfollow, in October 2005.
Whilst at ground level, the building is now surrounded by building sites for the crossrail project, and has had its odd fountains removed, it is still very visible from all around Central London. Look up, and you'll probably see it.
For more, see http://en.wikipedia.org/wiki/Centre_Point