Dejan B.
Google
The University tower stands in the corner of the University square between the Sao Miguel Chapel and University Palace.
It is not included in your combo ticket, but with it you pay only 50 cents to climb it.
I must emphasize I climbed many towers all over Europe, and this one by far has the narrowest staircase I've ever seen. In the upper part it is impossible to bypass other visitors, therefore they have staff at the bottom and at the top which communicate when people can go. For that reason people with claustrophobic and mobility issues should avoid it.
Once up, you have amazing views of entire Coimbra and further countryside, as the University plateau is already on top of a hill.