Cellular antennas are everywhere to be found on top of buildings these days. Those vertically long white antennas, usually three at a time pointing in different directions. But little is known how they look like on the inside. And there must be quite something in them these days as most of them support several independent frequency ranges and also two polarizations per antenna (horizontal and vertical) for MIMO and RX/TX diversity. I've had a number of posts on this blog on antennas over the years and my two favorites are 'Antenna in Ruins' and 'Antenna Stuff'. But so far I've never seen the inside of one. But recently I stumbled over a picture taken in the German Technical Museum and available on Wikipedia here that shows how it looks inside.