Atlanta has one of the most well-preserved AT&T Long Lines microwave towers, complete with a full array of KS-15676 horn antennas, that I’ve seen in quite a while. 
Of course, I’m disappointed by the modern deathstar logo; should be a proper Bell System logo. Also, I’m not sure what the round horns on the right corner are.
The KS-15676 horns were truly amazing antennas. They operated on multiple microwave bands with > 40dB return loss and had enough side isolation that relay stations could repeat on the SAME frequencies for receive and transmit.
The Long Lines Terrestrial microwave network was abandoned decades ago, but you still see a fair number of the KS horn antennas around because there’s no easy way to remove them.
At “hardened” facilities, the horn antennas were equipped with “blast kits” designed (aspirationally) to withstand the pressure wave from a nuclear explosion.
Anyway, I’m a sucker for vestigial artifacts of obsolete communications networks. Another example, still commonly intact out west, are railroad telegraph “code lines”.
For example,
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