Arecibo Observatory Radio Telescope, National Astronomy And Ionosphere Center, Arecibo, Puerto Rico

The observatory's 305 m (1,000 ft) radio telescope is the largest single-aperture telescope (cf. multiple aperture telescope) ever constructed. It carries out three major areas of research: radio astronomy, aeronomy (using both the 305 m telescope and the observatory's lidar facility), and radar astronomy observations of Solar System objects. Scientists who want to use the telescope submit proposals, which are evaluated by an independent board.
Visually distinctive, the telescope makes frequent appearances in motion picture and television productions. The telescope received additional international recognition in 1999 when it began to collect data for the SETI@home project.
The center was listed on the U.S. National Register of Historic Places in 2008. It was the featured listing in the National Park Service's weekly list of October 3, 2008. The center was named an IEEE Milestone in 2001.