Puente de San Martin was constructed in 1380 based on a commission by Archbishop Pedro Tenorio. The five-arch, Gothic style bridge is an impressive engineering feat for the Middle Ages. The center span is 131 feet wide and 88.5 feet tall. At either end are massive towers crowned with battlements. These offered protection against attacks by water for the west end of town. The medieval bridge crosses the River Tagus, the longest in the Iberian Peninsula at 645 miles.