W. M. Keck Observatory

The twin domes of the W. M. Keck Observatory near the summit of Maunakea on Hawaii's Big Island. Each houses a telescope whose 10-meter primary mirror is built from 36 hexagonal segments working as one piece of glass, with sensors and actuators holding each segment in place relative to its neighbors. The 13,796-foot summit has no nearby mountain ranges to stir up the upper atmosphere, which is why so many observatories share this one volcanic peak.