Foundation stone in the form of a letter labyrinth: Silo princeps fecit
Painting of Salvador Dalí inspired by the foundation stone.
The church contains a foundation stone in the form of a letter labyrinth ("Silo Princeps Fecit") that records the 8th-century founding of the church by King Silo of Asturias. The inscription Silo princeps fecit singularly combined in fifteen horizontal lines and nineteen perpendicular columns of letters. The T forms the beginning and the end of the first and last line in consequence of which the name Silo is not to be found till the eighth line and the S which begins it is exactly in the centre of that line and of the tenth column thus the name is in the shape of a cross as the letters above below and on each side of the S form the word Silo.
This letter labyrinth appears to inspire the hypercube of Salvador Dalí's painting A Propos of the "Treatise on Cubic Form" by Juan de Herrera, housed in the Museo Reina Sofia, Madrid.