Finish packing, check travel documents (visa, passport) and drive or taxi to Bloemfontein airport to connect to the Johannesburg flight; allow extra time for security and check-in.
Walk the palace grounds (Schloss Karlsruhe) and Schlossgarten to get oriented and enjoy a relaxed first afternoon; easy, scenic introduction to the city.
Try regional Baden cuisine — seek out a traditional Gasthaus or a restaurant near the Marktplatz for spaetzle, schnitzel and Baden wine; many restaurants open 6:00–10:00pm.
Visit the Cathedral (view the astronomical clock) and take a 1-hour boat tour on the Ill River to see the city from the water; many tours operate 10:00–17:00 depending on season.
Take a regional train to a nearby Rhine wine village (e.g., Rüdesheim area or smaller local vineyards) for tastings and scenic views; travel time varies (1–2h).
Check out and travel to Frankfurt Airport via direct ICE trains from Karlsruhe Hbf (approx. 1h–1h30); allow 2–3 hours for airport arrival before long-haul flights.