A two-level arcaded promenade designed in the late 18th century by Olaguíbel to bridge the difference in level between the medieval hill town and the new neoclassical city below. The lower arcade looks onto the Plaza del Machete; the upper one opens at the level of the old town walls.
It is one of the more elegant pieces of late-baroque urban engineering in northern Spain — a neat solution to a tricky site that gave the city a new public space without flattening anything. Wander through and notice the bronze plaques recording the names of fallen 19th-century mayors.