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The Post Office Tower (BT Tower)

Known as the Post Office Tower when first opened in 1965, this is now known as the British Telecom Tower or BT Tower.

It was the first purpose-built tower to transmit high frequency radio waves, and it serves as a functional telecommunications centre designed to relay broadcast, Internet and telephone information around the world.

It stands 188 metres high and has 34 floors. Despite the being one of most recognisable and conspicuous landmarks in London, it was classed as an 'official secret' for almost 30 years. The tower was even omitted from all Ordnance Survey maps until the mid 1990's.