Locomotive tender car question

Why do locomotive tender cars have cupolas? Are they occupied during runs? Sorry to sound ignorant but I'm an aviation guy.
A Place for Those Born Too Late...
http://coloradonewmexicosteamtrain.org/FriendsForum/
http://coloradonewmexicosteamtrain.org/FriendsForum/viewtopic.php?f=1&t=2942
Lynn Taubeneck wrote:PS Jason, I live in Fort Worth, we are practically neighbors!!!