Tour Eqho (also known as Tour IBM, and Tour Descartes) is an office skyscraper located in La Défense business district situated west of Paris, France.. Built in 1988, the tower, with a height of 130 meters, belongs to the third generation of towers in La Défense. The tower takes the shape of a parallelepiped in which a semi-cylinder would have been extruded on the main façade.