Third Avenue is an interesting avenue. I remember reading once in the Village Voice that Third Avenue was boring from start to finish, but I never thought that. My experience of it, at that time, was from 17th Street to usually not past 48th Street. Later it extended down to Prince Street, name-change* and all.
There are probably more new, tall buildings beside old, short ones than there are hovering over them, but this is not an uncommon sight. The wikipedia article on “Air Rights” shows a similar building configuration on Third Avenue.
It looks like only the yellow building on the right sold their air rights; the new building isn’t over the brown building. I suspect this means the yellow building is landmarked, and the brown building isn’t. But who knows?
* It becomes The Bowery at 4th Street.