B A R R Y wrote:

Some very large Bravo airports here in the east only have one tower,
as the only folks who need to be in the cab are the controllers who
need to physically see the field. Everyone else (approach / departure
/ enroute, FSS, etc...) can be in the basement or even a different
building.

DFW is sprawling. Your options are to make the tower way tall, and
way big so you can fit all the controllers in it such that they can
see everything, or you can distribute things.

When Dulles's new 300+ foot tower becomes operational, it will have
three sets of local (tower) and ground controllers working in it as
well as clearance delivery and supervisory positions. That will
be in addition to the existing ramp tower which controls traffic
pretty much between the terminals and the one on the Udvar-Hazy
tower which serves no useful function other than being a great place
to watch arrivals (now if I could just get them to put real ATC
audio and maybe a live radar feed, the exhibit has a prerecorded
one from EWR of all places).