For thousands of years, bridges have helped man to overcome his natural limitations. In the beginning it was only a tree that was laid over a stream, or stones laid into the water to cross smaller rivers. Later, simple hanging constructions made of natural materials followed, up to large stone bridges to cross large rivers and deep valleys. Today, bridges are masterpieces of modern construction technology and inspire the imagination of great engineers and architects as well as the admiration of the people who use them every day.