It's canary yellow, the size of a Volkswagen Beetle, and weighs nearly three tons.

Located on a tower near Seattle’s Woodland Park Zoo, it's one of the biggest air raid sirens ever built.

It's silent now, but from the early 1950s to the early 1970s, the siren went off every Wednesday at noon. It was loud enough to be heard a mile and half away.

The students at the John B. Allen elementary school right next door — today the Phinney Neighborhood Association — would scramble under their desks, cover their heads and practice their "duck and cover" techniques.

At the time, it was one of 21 air raid siren towers in Seattle (one other also remains at Northacres Park).

They were erected in response “to the Cold War, communists, and the threat of nuclear annihilation," according to a post in the Vintage West Woodland blog.

When the city considered where to install this particular siren tower, the topic came up at a Seattle School Board meeting.