Hwangnyongsa has pretty much won, but we all know the real winner was the Serpent Mound.
Not me
However, here are my suggestions:
Arc de Triomphe (Paris, France)
Castel del Monte (Italy)
Castel Sant'Angelo/Mausoleum of Hadrian (Rome, Italy)
Château Frontenac (Quebec, Canada)
Etemenanki/Tower of Babel (Iraq)
Galata Tower (Istanbul, Turkey)
Grand Bazaar (Istanbul, Turkey)
Ještěd Tower (Czech Republic)
Lotus Temple (Delhi, India)
Národní Divadlo/National Theatre (Prague, Czech Republic)
Pilgrimage Church of Saint John of Nepomuk (Czech Republic)
Pont du Gard (France)
St. Barbara's Church (Kutná Hora, Czech Republic)
Also, some Las Vegas Casino would be interesting - I propose the Sands. I know it doesn't exist anymore, but it was quite famous (for Frank Sinatra, for example).