IMPORTANT NOTE: The viewing deck and restaurant at the Grande Arche are PERMANENTLY CLOSED. This fact is extremely difficult to discover, since their website doesn't mention it and there is no sign whatsoever once you arrive; just an abandoned-looking welcome kiosk and decrepit public elevators with a half-ripped off sign that says they are out of service, but doesn't mention whether or not there is an alternate route up. We finally confirmed that it was closed by loading up Wikipedia on our phones and finding a small note that isn't mentioned on the Grande Arche's website:
"(After a non-injury accident in the elevators in April 2010, the Department of Ecology, owner of the roof of the Grande Arche, has decided to permanently close the computer museum, restaurant, and viewing deck. Access to the roof is still possible via the elevators in the north and south walls, but they are closed to the public.)" read more