On Our Travels with Darcy's Postcard Challenge - Switzerland

My daughter lives and works in Basel so I started there with my research. I found that one of the world's greatest mathematicians was born there, so as an ex Maths teacher that was irresistible. His name is Leonard Euler ( pronounced oiler) and he lived from 1707 to 1783. He laid the foundations of Calculus, Topology and Graph Theory. A giant on whose shoulders others stand. One of the famous  things he did was address the problem of the 7 bridges of Konigsberg. In that city there were 7 bridges and people were trying to walk round it crossing each bridge once and only once. Can it be done?
My postcard shows the map of the bridges and a portrait of Euler. I zentangled in his name.
My book page is the cover of one of his books and the pocket a 10 Franc Swiss bank note which shows his picture.
Thank you all for your kind comments over the last few weeks.
Jen x