I would like to start a thread about "well-kept" secrets of European airports. I can personally start with contributing two discoveries about Helsinki Vantaa airport (HEL) I have made during last year.

HEL
SHOWERS: there arent any public showers at Vantaa airport, but Scandic Gateway hotel (which is located just below the terminal 2) will allow you to use their sauna if it is free. Cost is 7 euros and towels and shaving equipments are included).
FOOD: about 15 meters from Scandic Gateway hotel reception desk is simple self-service restaurant (cant remember its name) which seems to be quite popular amongst airport workers and crew members. And for reason: main course (often home-cooked Finnish meal like meatballs or something) + green salad + juice/water + bread + coffee will cost only 6...8 euros and food is usually really good.

If you have any similiar hints or suggestions which can make transferring at ARN, FRA, VIE, MUC, LHR, AMS, CDG or at other major European airports more pleasurable, then perhaps you could post them here.