Truth be told, I’ve never seen this island or monument in my life until today when I ran into it on Google. Yet its been in the middle of Biscayne Bay for more than 90 years or so. What actually sparked the search was when I posted that aerial of Star Island and noticed the small white island in background.
But yeah, Flagler Monument Island is a manmade island located alongside the other Venetian Islands of Miami and Miami Beach. A 110-foot (34 m) high obelisk with allegorical sculptures at its base stands as a monument to Miami pioneer Henry M. Flagler, and was constructed in the center of the freshly constructed island in memory of Flagler, who died in 1913.