Travelled through the Frankfurter Kreuz (Frankfurt Interchange) recently and I noticed that a number of the cities cited on the direction boards were a considerable distance from Frankfurt:
Basel - 329 km
Munich - 393 km
Cologne - 193 km
Hannover - 413 km
These are not as far as the 525 km noted by JohnnyMo, but are of the same order of magnitude and moreover are all in different directions.
There are signs from the Berliner Ring towards Poland on the A12 giving the distance to Warsaw - which is around 550km or so from the Ring.
Distances of 600-700km aren't uncommon on signs here, too - for instance, Terespol (on the Polish-Belarusian border) is signed all along the A2 motorway from the German border, as is Korczowa (Polish-Ukrainian) from the Polish-German border. Distances are normally given to where the road terminates - so distances of 600-700km in Poland are ordinary.
(of course, the policy on signing cities abroad is all over the place - signs are appearing for L'viv on the A4, but frequently, only the border crossing is signed and nothing else. For instance - in Poznan - Swiecko, population 180 is signed - and not Berlin or even Frankfurt (Oder))