Train
The Mathematical Institute can easily be reached on foot from the train station Köln Süd which is one or two stops from Cologne's central train station Köln Hbf by regional trains (RE, RB).
Plane
The closest airports are Cologne Bonn Airport (CGN) and Düsseldorf Airport (DUS), but there are also direct trains between Cologne and Germany's largest airport Frankfurt Airport (FRA).
The Mathematical Institute is located in the main campus of the University of Cologne.