The Keystones of the Cross Vaults of the Lonja de Valencia (Spain). Graphical Analysis of the Geometry of the Polar Keystone of the Starry Vault of the Chapel

Abstract

The Lonja de la Seda of the city of Valencia is one of the best examples of Spanish civil Gothic-style. It was built between 1483 and 1498 and it has cross vaults in the columnary hall and in the adjacent Chapel. The keystones of these vaults are the object of the present paper together with an in-depth geometric analysis of the central or polar keystone of the starry vault of the Chapel. These keystones were studied by the author of this communication in her doctoral thesis. The research provides information on the shape and dimensions of the keystones, the way of tracing and constructing them and the way in which the ribs converge. Aspects related to the design and construction of cross vaults as well as the measurement units used in its construction and other metric and geometric relationships will also be analysed or dealt with. The representation in two and three dimensions of the polar keystone of the vault of the Chapel is included in the paper as well as the representation of the profile of the ribs that reach it and how to join them so that they are flush with the extrados. It also reflects the measurement unit used in the construction of the vault derived from the maximum diameter of the keystone: a Valencian vara of 90.6 cm equivalent to 4 Valencian spans of 22.65 cm and other geometric relationships.