Paris Metro

You'll sweat in the hot and crowded coaches, while it is freezing outside.

Your endurance and strength will be put to a test if you decide to change lines in Chatalet with a lot of baggage.

You'll get stuck in the entrance gates since the infrared sensors won't recognise that you and your carry-on baggage would like to pass in one single piece.

And you will have to walk home or find yourself a taxi if you stay somewhere in Paris any later than 1AM.

But other than that, it is a great mode of transport.