everything begins with the cross ribbed vault: a vault based on a cross-shaped stone framework that facilitates the construction process. this practical form quickly became a leitmotif of gothic architecture, and as early as in the 13th century, architects attempted to vary this form in different ways. in 15th century central europe, the invention of new vault configurations became the main theme of architecture, and architects created incredibly imaginative “skies” floating over the walls and pillars of church and castle interiors. some experts claim that a series of incredibly complex loop-shaped rib vaults in surprisingly remote rural northern austria is the unsurpassed climax of gothic vaults. british, german, czech and slovenian scholars will vehemently disagree.