Commissioned by Alfonso II the Chaste, the Holy Chamber is the place that safeguards Asturias' most valuable treasures: the Cross of the Angels, symbol of the city of Oviedo, and the Victory Cross, a symbol of Asturias emblazoned on the flag. What is believed to be the Holy Shroud of Christ is also safeguarded here.
The Holy Chamber is rectangular and has two floors; the lower one, called the Chapel or Crypt of Santa Leocadia, is covered with a barrel vault supported on plinths with coarse lunettes, while the upper floor, the Chapel of San Miguel, is divided into three sections, retaining the original apse, while the rest dates from the second half of the 12th century. It is covered with a barrel vault reinforced with three transversal ribs supported on six limestone columns, to which pairs of statues of the twelve Apostles areaffixed.
Also embedded in the wall inside above the entrance door are three heads carved in stone, corresponding to a Crucifixion which originally also held painted bodies. Today, the painted part has totally disappeared.