The austerity of its exterior appearance, due to the fact that it was included in the city walls, does not allow us to guess the beauty and richness of its interior. This church has a splendid Gothic ensemble, the most important in the city after the Cathedral.
The first phase of the temple was carried out in the 13th century, but it was in the 15th and 16th centuries, when the city lived its period of splendour, that the second and definitive remodelling was carried out. During this period, magnificent sepulchral chapels were built by artists such as the Colonia, Juan de Vallejo, Felipe Vigarny, Gil and Diego de Siloé. The chapels of the Nativity of Mary, Our Lady of the Good Morning and the Chapel of the Kings stand out.
The main chapel has a 17th century altarpiece by Policarpo de la Nestosa. The central section is occupied by a large 18th century painting of Saint Giles, the work of the Burgos painter Martínez Barranco. Likewise, on both sides we find Ferdinand III, The Saint, and his cousin Saint Louis of France. The altarpiece is crowned by a 17th century crucifix.
The stained-glass windows in the apse were made in 1928. The one on the left represents the miracle of the Holy Drops and the one on the right shows St. Giles being fed by the hind.
The Holy Christ of Burgos is venerated here. This image was in the now disappeared convent of the Holy Trinity. With the confiscation of Mendizábal, in 1835, the monks were expelled and the image was transferred to the parish church of St. Giles.
Next to the church stands the so-called Arch of St. Giles, which served as a defensive tower and prison until the 16th century.