There was a German architect who devoted his whole life to promote his grand scheme of damming and draining the Mediterranean to create vast amounts of land and to unite Europe and Africa into one super continent.
Home of Truth, Utah was a religious utopian community in the 1930s whose leader claimed to receive divine revelations through her typewriter.
There was a man-made mouse utopia called Universe 25. It started with 4 males and 4 females. The colony peaked at 2200 and from there declined to extinction. Once a tipping point was reached, the mice lost instinctual behaviors. Scientists extrapolate this model to humans on earth.