The urban landscape of Paris revolves around the Seine, which crosses the city from east to west over nearly thirteen kilometres, with a width varying between thirty and two hundred metres. It is spanned by thirty-seven bridges, including four pedestrian bridges that link its more extensive right bank to its left bank. According to geographical reality, it is not the Seine but the Yonne that flows through Paris, the flow of the Yonne being greater than that of the Seine at their confluence, but the historically sacred nature of the Seine has earned it this usurpation.