The COP21 will be held at Le Bourget airport, north east of Paris.
Getting there: Le Bourget is accessible from central Paris by special direct buses from the Gare du Nord train station and by the RER B metro-train. Taxis and transportation services can drop and pick-up passengers and will be in very high demand. Private cars are not recommended.
A helpful map of the Public Transport network is available here:
Getting around: there will be 3 zones dedicated to COP21 on Le Bourget site
The COP21 Conference Centre (Blue Zone) – the official UNFCCC meeting area where all of the negotiations and official side events will take place, only accessible with UNFCCC badges
The Espace Generation Climat (Civil Society Green Zone) – open to the public to showcase their climate activities, no UNFCCC badge needed
La Galerie – a dedicated area for business, commercially run by Reed Exhibitions, no UNFCCC badge needed
The Blue and Green Zones are connected by a walkway, whereas the Galerie is a shuttle bus away.