This altarpiece consists of two separate elements: the principal part, which would have hung on the wall above the altar and below and, in front of it, the frontal or antipendium. The former, which is pentagonal, is divided vertically into three sections. The central one housed images of the titular saint and the Crucifixion above, now lost. Both parts of the altarpiece, which comes from León, depict episodes from the life of John the Baptist.