I am working on my trip report and have come to a Florentine landmark I can't name.

It is a tall tower of three arches (one atop the next) in what appears to be brick. It's on the way up to the Piazzale Michelangelo. I've checked guidebooks somewhat extensively, but no luck.

Can someone tell me the name of this structure?

The only tower that I can think of on that side of the Arno is the one at the Porta San Niccolo. In one of my illustrated (with drawings, not photographs) guidebooks to Florence, it is shown as having one arch at the bottom, two rows of small openings (presumably to shoot arrows from), a top row of what look like narrow arched openings (the spine of the book makes it hard to see exactly what they are), the whole thing topped off by the indentations that my dictionary calls either a (singular) battlement or (alternating) crenels and merlons.

Aha! That's it! Thanks Eloise. Since I now had the name, I found this image:

http://www.firenze-oltrarno.net/immagini/psnicc2.jpg

which looks just like our picture!
Koshka

I'm delighted I was able to help. Now I wonder where the author/illustrator of my guidebook got his very different version from...

I think it looks completely different from the Arno side. Try entering "Porta San Niccolo" into the google image search option. You'll find a number of views of it.

Thanks again!