Yellow-bellied sliders (Trachemys scripta scripta). The Olmense Zoo has quite a lot of these in several ponds and moats (this one by the restaurant, the capuchin island moat, two ponds in the Tropics hall et cetera).
I originally identified this turtle as a Cumberland slider, but it is actually a yellow-bellied slider. I apologize for the mis-identification. Thanks to wally war eagle for helping me to correct the identification.
