The roofing of wide spaces presented a challenge to the medieval builder which resulted in some of the most impressive creations of the middle ages. The architecture of ancient Rome had provided precedents for different types of stone vaulting. Vaults continued to be constructed over small spaces, but in England in the early middle ages large spans had timber roofs, developing the practices known to have been established as early as the 7th century for the great timber halls of the Anglo-Saxons. Timber roofs achieved great sophistication in the 14th and 15th centuries, using a variety of techniques to cover wide spans.