	York was a Viking capital in the 10th century, and continued as an important northern city in the 11th century. In 1068, on William the Conqueror's first northern expedition after the Norman Conquest, he built a number of castles across the north-east of England, including one at York. This first castle at York was a basic wooden motte and bailey castle built between the rivers Ouse and Foss on the site of the present-day York Castle. It was built in haste; contemporary accounts imply it was constructed in only eight days, although this assertion has been challenged. The motte was originally around 200 feet (61 metres) wide at the base. As it was built in an urban environment, hundreds of houses had to be destroyed to make way for the development. William Malet, the sheriff of Yorkshire, was placed in charge of the castle and successfully defended it against an immediate uprising by the local population.