Upvote:1
I know for sure that the bus stops at Nice airport which is where I took it from.
Upvote:3
According to both the bus schedule for line 21 on the regional bus authority (LER)'s website, and to the Castellane tourism office website, the bus leaves from the gare routière (bus station).
There is an information desk on Avenue des Diables Bleus (gare routière de Saint-Jean d'Angély) [Google Maps]. This is also the address given by LER. It is located near the Nice-Riquier train station, not close to the main train station.
The historic building was demolished in 2011 and the bus stops were spread out over several sites, so don't set any store to information older than 2011. I can't find any more recent news in the local paper. Do note that some local buses around this sector are being deviated.
Beware that I'm not a local, I'm only reporting what information I could find on the web (in French). If nobody can come up with better information, you may want to scout out the day before or ask at a local tourist information desk. And please report your findings here!
There is only one bus at 7 in the morning, and another bus at 14:40 except Sundays and holidays (this region is not friendly to travelers without a car). Don't miss it!