"What does it mean to have an imaginary exponent?" This site has an exceptional answer and explains it in two different ways

This lesson focuses on developing a way to cross all 7 Bridges of Konigsberg without crossing any of them more than once. Euler discovered it was impossible, but he developed the idea of using graph theory to determine if it would be...

This site gives a general description of one of Euler's contributions, topology. It also presents one of the more famous problems of mathematics, The Bridges of Konigsberg.

A portrait of Leonhard Euler from the Dibner Library of the History of Science and Technology, made available through the Smithsonian Institution's Scientific Identity Collection.