Weird round tower things..what are they

[SarcasticDwarf]

So my family is driving back to Wisconsin through St Louis (posting from my phone) and there are a pair of weird towers just west of the city limits. They look like small oil tanks with a steel ring about four stories tall placed around the edge. Anyone know what these are?

 

[K1052]

http://en.wikipedia.org/wiki/Gasometer

 

[LordMorpheus]

variable volume natural gas storage, I think.

 

[IronWing]

Yep. I knew what the OP was talking about from just the thread title.