The days of putting your ear to the ground detect approaching cavalry are over. Now nations sport systems like the Iron Dome, THAAD radar, and these nine all-seeing early warning systems from our friends at Oobject. Really, there's no use hiding.
WW1 concrete mirror, early warning against Zepellin attacks
In the original designs of these acoustic mirror, a curved recess in the concrete bounced sound towards a listener wearing a stethoscope.
Abandoned Tropospheric Scatter Dishes, once part of NATO ACE HIGH communication system
Teufelsberg (Devils Mountain) listening station, overlooking Berlin
Duga-3 array within Chernobyl exclusion zone, responsible for the infamous Woodpecker signal
The Woodpecker signal was a mysterious repetitive short wave radio frequency emanating from the Soviet Union during the Cold War. It later turned out to be part of a long range early warning system based in Ukraine.
Infra red detecting satellite as part of DSP early warning system
One of 23 satellites in this system, which can detect the heat signature of missile launches. Shown here, being deployed from the Shuttle.
Sea Based X-Band Radar
A floating radar platform that is used, among other things, to detect North Korean missile launches, from it usual home in the Pacific.
Airborne Early Warning and Control (shown here, China's)
Abandoned Dye-2 early warning radar base, Greenland
Part of the Distant Early Warning or DEW line, against a Soviet airborne or land based attack over Canada.