Air traffic control towers always have windows that slope toward the tower at the base. Many people assume that they are designed that way to prevent the sun's reflection or glare from blinding incoming pilots.
The benefit is not for those outside the tower, but those inside it.
Ordinarily, we see reflections in glass all the time, as from
computer screens, TVs, or car windows. Air traffic controllers must
not have any distracting reflections as they monitor flights. By
tilting the glass away, any errant light from inside the tower, such
as video screens, lights, etc. are reflected up onto the ceiling,
which is painted black.