Barcelona once for El Classico Sat right up in the gods. would have had a better view on TV lol for someone who doesn't like heights it's a scarily steep stadium but the atmosphere was something else. Other than that it would be Portsmouth or Southampton away i think, not sure which is further.
Athens for a European game. All in one day too, flew out about 5am, 4 hour flight, game kicked off 6pm UK time, got back into my bed about 4am. 1650 miles from home as the crow flies according to Google.