Visitors travelling by plane will arrive at one of the international airports in Frankfurt, Stuttgart or Karlsruhe/Baden-Baden.

Arrival at Frankfurt International Airport:

Frankfurt Airport is well connected to Karlsruhe Hauptbahnhof (main station) via long distance trains.
See here for time tables: DB Bahn

Arrival at Stuttgart Airport:

Take tram line S2 or S3 to Stuttgart Hauptbahnhof (main station). A train will take you to Karlsruhe Hauptbahnhof (main station).
See here for time tables: DB Bahn

Karlsruhe/Baden-Baden Airport (Baden-Airpark):

Do not try to fly here unless you happen to find a very good connection and/or cheap flight.

Take a bus from Karlsruhe/Baden-Baden Airport the train stations of Rastatt or Baden-Baden. From there you will be able to get to Karlsruhe Hauptbahnhof (main station)by train.
See here for time tables: DB Bahn

Alternatively you might try the Baden-Airpark-Express which will take you directly to Karlsruhe Hauptbahnhof.

Coming from Germany or other European countries the most convenient way to get here might be by train. ICE and international trains stop at Karlsruhe Hauptbahnhof (Karlsruhe Main Station). There are direct train connections for example from to/from Paris, Zürich, Amsterdam, Frankfurt, Stuttgart, Cologne or Munich.

See here for time tables: DB Bahn

Coming from France you can directly search on the SNCF site.

The fastest and easiest way to get around in Karlsruhe (other than walking) is the tram. The tram station "Kronenplatz" or "Kronenplatz (Fritz-Erler-Strasse)" is closest to the math building.

On the day of your arrival, you will need a ticket for the tram. You can either buy this as an extension of your long distance rail ticket from German Rail (ask for a City mobil-extension when buying the train ticket to Karlsruhe at a counter) or at one of the vending machines at the tram stations.

See here for time tables: KVV