This derelict round tank, called the 'Morton Sphere', is part of the old Gopher Ordnance Works ruins - a long abandoned World War II era gun powder factory south of the Twin Cities in Rosemount, MN. The plant just started production when the war ended in 1945 and everything was shut down.
More than you probably want to know:
The University of Minnesota took over the Gopher Ordnance Works property and renamed it ‘UMore Park’ (That's 'industrial' park and not 'play' park because a big chunk of the place is still contaminated). Currently, the U of M’s Agricultural Research Station and the Dakota County Technical College are located on part of the site.
The Morton Sphere was used to hold anhydrous ammonia during the GOW (Gopher Ordnance Works) days and later for the University’s supersonic wind tunnel research. It sits empty and rusting now.
Thanks to my very smart friend Ralph who sent me info as to why it's called a Morton Sphere; apparently a person called Pierce Morton confirmed the focus-directrix property in 1829 that has something to do with geometric conic sections that include mathematically induced round shapes called dandelin spheres. The brainiacs that created this thing probably read Pierce’s books for fun and named this sphere after him – mystery solved, thanks Ralph!!