法國自由行

Gare du Nord 和 Gare de Lyon 之間, 你需要預算約 30 - 40 分鐘搭 metro. 在 Gare du Nord 搭 5 線 metro 去 Bastilles, 然後再轉 1 線去 Gare de Lyon 就是了.
Gare du Nord 和 Gare de Lyon 都是在 zone 1 的. 普通的 metro 票便 ok 了
根據你的行程, 其實你只需來回巴黎和阿維農, 只是 2 程火車. 不用買火車證了...

my suggestion is stick to the metro and don't take the RER, especially if this is your first time in paris. i don't know how that RER works when i was there and i was forced to use 3 tickets to complete the trip when i could have used just one if i have sticked to the metro only!

And you can try to check in ratp.fr because this is the tranfic company in france and I think you can take line 4 from Gare de Nord to Les Halles after change the RER A direction is Boissy-st-Léger or Marne-la-Vallée. Is more faster, I think not more than 25mins.