The border could be crossed legally only through a limited number of air, road, rail and river routes. Travellers to and from Denmark, Sweden, Poland and Czechoslovakia could also pass through East Germany. Access rights for non-Germans were otherwise very restricted. Foreigners had to submit an itinerary to the East German state tourist office up to nine weeks in advance, paying booking fees and registering with the local police on arrival, purchasing fuel only from specially approved petrol stations and spending a prescribed minimum of money each day. They were required to stay in state-owned "Interhotels" where rooms cost five to ten times more than in the (very few) ordinary East German hotels. Not surprisingly, East Germany did not develop much of a tourist industry; even as late as M