octagonal towers: Torre de Cristal (Madrid) and 1 World Trade Center (NYC). Crystal Tower began construction in 2004 and this iteration of the "Freedom Tower" was unveiled in 2005.

Torre de Cristal, Cuatro Torres Business Area, Madrid by Gaspar Serrano, on Flickr

One World Trade Center by Jakub Slováček, on Flickr

Torre de Cristal, Cuatro Torres Business Area, Madrid by Gaspar Serrano, on Flickr

One World Trade Center by Jakub Slováček, on Flickr