Church of Santa Marta de Tera, Romanesque church in Santa Marta de Tera, Camarzana de Tera, Spain

The Church of Santa Marta de Tera is built of large, regularly cut slate blocks, with sandstone reserved for sculpture. It has a Latin-cross plan, a three-bay nave, a square apse closed by a straight wall inside and out, and a square lantern over the crossing. Under the roof, 199 corbels show animals, leaves, pine cones and human figures.

A monastery dedicated to Saint Martha existed here by 979, the date of its earliest surviving document, and its first abbot was named Julián. In 1063 Ferdinand I and Queen Sancha gave it to Bishop Ordoño of Astorga; the present church was built between 1085 and 1129, and a 12th-century fire destroyed part of the nave and west portal. Alfonso VIII visited in 1129 to give thanks for a cure.

The monastery was dedicated to Saint Martha of Astorga, and the church keeps that dedication. In 1129 Alfonso VIII of León visited to give thanks for recovery from a serious illness and confirmed the monastery's independence from any lordship. The south portal shows Saint James the Elder as a pilgrim, with staff, satchel and scallop shell.

The church stands on the Vía de la Plata, 27 km west of Benavente and about 89 km north of Zamora, in the centre of the Tera valley at the eastern edge of the Sierra de la Culebra. The south portal is the main entrance, with a smaller door in the north transept arm and a heavily restored one at the west end. To see the equinoctial light, come around 21 March or 21 September, when a ray enters through the central oculus of the apse and falls on the carved capital to the left of the apse.

Twice a year, at the spring and autumn equinoxes, a shaft of sunlight enters through the oculus of the apse and falls on the carved capital left of the apse, known as the "just soul": a sexless figure in a mandorla carried up by two angels. The effect is called the "miracle of the equinoctial light".