On the contrary, I found plenty to do during siesta time, with the caveat being you need to research opening hours ahead of time. Not everything will be open mid-afternoon, but usually 1-2 attractions remain open and that's enough to keep you occupied with careful planning. Other options include buying picnic supplies ahead of time in the morning and then dining al fresco while everything shuts down anyway or simply walking through neighborhoods to take in the architecture, etc. I wouldn't worry too much about siesta.
In Cordoba, I was able to see the Mezquita, Medina Azahara, and walking through Old City & the Roman Bridge into a day without feeling rushed in the slightest. Of course everyone travels at a different pace and there is more to see/do should you have time, which Wandrlst88 does not.