(CNN) A US government agency dedicated to the development of top-secret military technologies has a pressing need: an underground lair. And they need it by close of business today.

The Defense Advanced Research Projects Agency, better known as DARPA, tweeted the appeal Wednesday.

"Attention, city dwellers!" the tweet read. "We're interested in identifying university-owned or commercially managed underground urban tunnels & facilities able to host research & experimentation."

"It's short notice," they admitted. "We're asking for responses by Aug. 30 at 5:00 PM ET."

Attached to it were a series of photos -- a dimly lit parking garage, an underground bunker with Polish signage, and an empty subway station -- and a link to the formal proposal on a government website.

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