List of highest astronomical observatories

Prior to the late 19th century, almost all astronomical observatories throughout history were located at modest elevations, often close to cities and educational institutions for the simple reason of convenience.

[2] The first high altitude observatory was constructed atop the 2,877 m (9,439 ft) Pic du Midi de Bigorre in the French Pyrenees starting in 1878, with its first telescope and dome installed in 1904.

Among the largest, best developed, and most renowned of these high altitude sites is the Mauna Kea Observatory located near the summit of a 4,205 m (13,796 ft) volcano on the Island of Hawaii, which has grown to include over a dozen major telescopes during the four decades since it was founded.

Sites at high altitude are ideal for optical astronomy and provide optimal seeing, being above a significant portion of the Earth's atmosphere with its associated weather, turbulence, and diminished clarity.

In particular, sites on mountaintops within about 80 km (50 mi) of the ocean often have excellent observing conditions above a stable inversion layer throughout much of the year.