Calahorra is a municipality in the Spanish autonomous community and province of La Rioja. During Ancient Roman times, Calahorra was a …Calahorra is a municipality in the Spanish autonomous community and province of La Rioja. During Ancient Roman times, Calahorra was a municipium known as Calagurris Nassica Iulia. The city is located on a hill at an altitude of 358 metres at the confluence of the Ebro and Cidacos rivers, and has an area of 91.41 km². Calahorra is the second-largest city in La Rioja in population and importance, after the capital, Logroño. Its population is 23,923 people.