British Airways Jumbo Jet flying away from Heathrow, London, United Kingdom

"Vierzylinder" (four-cylinder engine), BMW head office with museum, Munich, Bavaria, Germany

Locomotive letting off steam, detail view of four-coupler hot steam locomotive, ELNA 6 type of 1930, Ebermannstadt, Upper Franconia, Germany, Europe

Wheel drive of a four-coupler hot steam locomotive, ELNA 6 type from 1930, works number 9963 of Berlin Maschinenbau-Actiengesellschaft, still in use in Ebermannstadt, Upper Franconia, Germany, Europe