Westerbork observatory

Near the village of Westerbork, about 30 min drive from our home, is this row of 14 antennas with a diameter of 25 meters each, and together they form one big (HUGE is a better word) telescope. Four of them are movable along 2 rail tracks. They are operated by ASTRON, the Dutch foundation for astronomy research. The telescopes are often combined with other ones around the world to perform certain observations.
Officially called the Westerbork Synthesis Radio Telescope (WSRT), it is commonly known as 'sterrenwacht Westerbork' ('Westerbork observatory').

Switch off your mobile phones

This warning sign along a sandy path in the centre of the Dwingelderveld National Park told us to switch off our mobile phones as we were entering the interference-free zone of the nearby Dwingeloo radio telescope...

...which we passed later that day. The "Dwingeloo Radio Observatory" is a single-dish radio telescope with a diameter of 25 m. Completed in 1956 it was the largest radio telescope in the world at that time, and was operational in an official capacity until the year 2000. Nowadays the telescope is a Dutch heritage monument, and is still used for projects by amateur astronomers and radio amateurs.

I'm linking to signs, signs.