This is the water clock on Tala'a Kbira in the Fez Medina, after which Cafe Clock is named. No one seems to know how it works; all that is known is that it is/was a clock.
I found a map of the Medina, and Cafe Clock is marked with a "5". My friend Evelyn's "dar" ("house") is on Derb Bensalem, two "blocks" from Cafe Clock. Note location of the Bab Boujloud, shown in this post from a couple of days ago.