The church occupies the most strategic place of the town; like a small fort, it dominates the territory and its steps from the height that gives the steep hill where Castañar de Ibor sits. It is the strongest place and most probably, the first embryo of the population.
The complex has four distinct parts: central nave, apse, tower and side naves (chapel and sacristy). The nave is rectangular, with an east-west orientation.
Strong masonry walls made mainly of slate, although quartz and quartzite are also used. Currently it has only one door with a semicircular arch on the north side, however, formerly there was another entrance on the opposite side, this one has a curious ogee arch that resembles those of the Church of Cabañas del Castillo or Solana, among the closest ones. This one is very used from XI to XIII century, according to some testimonies, in the present door there would be another one equal to this one.
The ceiling has a beautiful coffered woodwork supported by two rows of columns, also made of wood. This makes the ship appear as if it were divided into three sections. The place for the large baptismal font, made of a single piece of granite, is the lower part of the tower.
The choir that occupies the back of the church is very large, from which the tower is accessed through a door that leads just above the baptistery. An iron staircase leads to the upper part where the bells and what is left of the clock mechanism are located.
Since the exteriors are painted white, it is not possible to appreciate many constructive aspects, but the interior of the tower shows the traces of other bell openings on lower levels.
Surely when the apse was built, the height of the tower was raised a few meters, giving more slenderness to the whole.
The apse is the great work carried out in the 16th century in the heat of the economic boom brought about by the American gold and the hegemony of the Spanish Crown in the world.
A few meters from the altar the famous Christ of the Avellaneda is exposed. A hyper-realistic carving from the 15th century, polychromed with great care and detail. It is a very original and rare specimen, it used to be in the Avellaneda and with the abandonment of the population it ended up in the church of Castañar.
There is also a pulpit completely polychromed, both inside and out: decorated with paintings of ancient tracery, representing the four fathers of the church: St. Jerome, St. Gregory, St. Augustine.
