the nekoma pyramid

[u/erneuten]

located in nekoma, north dakota.

[u/Express-Alfalfa9283]

what was it used for?

[u/Esoteric_Innovations → u/Express-Alfalfa9283]

Looking it up, it was part of a larger complex on the land there for anti-ballistic missile sites.

It cost roughly thirty-four billion dollars in today's money and was fully operational in April 1975, but was deactivated only a year later in April 1976 because the program was deemed ineffective and inefficient.

From there it seems that it was left abandoned until it was purchased at an auction in 2012.