What is this old plumbing fixture and can it go?
I've never seen one of these (old ones) myself, but following Ed Beal's comment on a different question it's probably "an early form of damper as it was full of air" which could be as "large 2" pipe tee after the main valve with a stubbed leg verticle for 4-6 feet". A bit of googling can find similarly tall (and old looking) ones, although perhaps not quite as tall as yours (n.b., the one below was labeled "primitive"):