One of the most characteristic buildings in the city of Zaragoza is la Lonja (the Contracting Exchange), used for dealing in agricultural products, especially grain. The building was constructed between 1541 and 1551 to ensure that all the dealings for the city were conducted in one place and not in public or religious places. It was one of the most important places of its time. The building is Renaissance in style with Florentine influence, having four equal sides with three floors, built in brick and slightly evoking the mudejar style. The first floor has large windows and elegant doors with half-pointed archways. The second floor is similar to the first, with circular windows inside the arches and the third floor has a typical Aragonese gallery with arches containing other smaller arches. decorated with circular medallions containing busts.

The inside of the Exchange is a square room made up of three naves with star-vaulted ceilings, held up by two dozen conical pillars. These pillars are decorated with gilt rosettes.

The Exchange, with its unusual design, half Gothic and half Plateresque adds its graceful presence to the illustrious past of this wonderful city.