Church of Gelsa Monument · Gelsa, Ribera Baja del Ebro, Zaragoza Church of San Pedro Apóstol in Gelsa, built in the last third of the 17th century reusing the walls of the old aljama mosque and remodelled in 1863; it holds the relic of the Santa Espina in a glass-and-gold reliquary. Photo: Zagri (CC BY-SA 4.0) What to see and do in Gelsa