The Large Millimeter Telescope (LMT) (Spanish: Gran Telescopio Milimétrico, or GTM) was inaugurated in Mexico on 22 November 2006. It is the world's largest and most sensitive single-aperture telescope in its frequency range, built for observing radio waves in the wave lengths from approximately 0.85 to 4 mm. It has an active surface with a diameter of 50 metres and 2000 m² of collecting area. It is located on top of the Sierra Negra, the fifth highest peak in Mexico and an extinct volcanic companion to Mexico's highest mountain, the Pico de Orizaba, in the state of Puebla. Its construction took 10 years, and cost 116 million dollars. It is a binational Mexican (80%) - American (20%) joint project of the Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE) and the University of Massachusetts Amherst.