Walk through some of central London’s most iconic areas and discover transport secrets hidden in plain sight. Walk a part of the Piccadilly line above ground and learn why it swerves and curves underground. Hear about the multitude of tunnels underground in the Holborn area, some of which are abandoned. Find out why you can hear trains running while walking in tranquil Embankment Gardens. Learn more about the first public transport thoroughfare of London; the river Thames..