Spire spires were an astounding architectural innovation, beginning with the early fourteenth-century spire at Freiburg Minster, in which the pierced stonework was held together by iron cramps. The openwork spire, according to Robert Bork, represents a "radical but logical extension of the Gothic tendency towards skeletal structure." The organic skeleton of Antoni Gaudi's phenomenal spires at the Sagrada Família in Barcelona represent an outgrowth of this Gothic tendency. Designed and begun by Gaudi in 1884, they were not completed until the 20th century. In England, "spire" immediately brings to mind Salisbury Cathedral. Its 403-foot (123-m) spire, built between 1320 and 1380,
Strasbourg Cathedral together represent some of the earliest uses of architectural drawing. The work of Professor Robert O. Bork of the University of Iowa suggests that the design of the Strasbourg façade, while seeming almost random in its complexity, can be constructed using a series of rotated octagons. The north tower, completed in 1439, was the world's tallest building from 1647 (when the spire of St. Mary's church, Stralsund burnt down) until 1874 (when the tower of St. Nikolai's Church in Hamburg was completed). The planned south tower was never built and as a result, with its characteristic asymmetrical form, the cathedral