Green Bank Observatory

The Green Bank Telescope has a dish about a hundred metres across and, unlike Arecibo, it steers - it is the largest fully steerable radio telescope anywhere, and its surface is made of over two thousand panels adjusted by actuators to hold the shape as the structure flexes. It sits inside the National Radio Quiet Zone, a thirty-four-thousand-square-kilometre area established in 1958 where transmissions are restricted by federal and state law; near the site mobile phones and wifi are prohibited outright and staff use diesel vehicles because petrol spark plugs generate interference. Visitors must switch devices off. The site also ran Project Ozma in 1960, the first modern search for radio signals from other civilisations.

What you'll find

• A steerable hundred-metre dish - the largest of its kind.
• Over two thousand adjustable panels - holding the surface shape.
• A legally enforced radio quiet zone - no phones or wifi near the site.
• The Project Ozma site - the first modern SETI search, 1960.

When to go

May to October for full tour schedules. Two to three hours.

Things to know

Phones and wireless devices must be off - not merely silenced - and this is enforced. There is no mobile signal in the valley regardless. Tours run on a schedule and reduce in winter. It is remote mountain driving to get there.

Nearby

Cass Scenic Railroad is south; Snowshoe is west.

Key facts