Criadillas are considered a more than one tourist-conscious menu bills them as mountain oysters, but they are in fact bulls' testicles.
Criadillas come from bulls slaughtered at local bullfights. 
mnli hypothesis: Criadillas come from bulls slaughtered at local bullfights.  premise: Criadillas are considered a more than one tourist-conscious menu bills them as mountain oysters, but they are in fact bulls' testicles.