Prague pneumatic post ( Czech : Pražská potrubní pošta ) is the world 's last preserved municipal pneumatic post system . It is an underground system of metal tubes under the wider centre of Prague , totaling about in length . The system started service in 1889 and remained in use by the government , banks and the media until it was rendered inoperative by the August 2002 European floods
2002 European floods
2002 European floods
Prague pneumatic post