Our Pick
Posted on @rawstates
The Graphite Reactor
1943
Oak Ridge, Tennessee
Public domain · Wikimedia Commons
The world's second nuclear reactor and the first built to run continuously, producing the first few grams of plutonium ever made in quantity. After the war it made medical isotopes, and the first shipment went out in 1946, the origin of nuclear medicine.
That was 1 of the hidden places.
Location: documented spot
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