I believe I once read that it is the flattest place on earth.
(since I'm in the mood to ramble and SSS is on a pedantic kick)
Levelest maybe, but not flattest.
Level would mean all surface points are the same distance from the magnetic center of the earth. Water would spread out evenly over it.
Flat would mean the surface followed a straight line from point A to point B, 75 miles away. Water would pool in the center but the water's surface would be level.
How's that for nit-pick'n?!!