IPGP
1, place Jussieu, Paris 5th arrondissement (metro stop "Jussieu", near the Jardin des Plantes)
Most of the meeting will be in room 108. You will need to get a "visitors" badge at the reception, then take the elevator or stairwell up to the 1st floor. From there, follow the signs to room 108.
OBS facility
65 ave du General du Gaulle, (20 minutes walk from RER A stop "Noisy Champs", direction "Marne La Vallée Chessy TGV")
Ten minutes further along the RER A is a train station with direct connections to Charles de Gaulle Airport
Hotel
We recommend you take a hotel near to IPGP or Les Halles. IPGP is 15-20 minutes walk fromthe Gare de Lyon RER A station (or you can take the #24 bus from the road along the Seine behind Jussieu). Les Halles is a hub for the RER A, B, C and D regional trains.
Transports
RER A heads from Paris (Gare de Lyon and Les Halles stations, among others) to the "Noisy Champs" station.
RER B heads from Paris (Les Halles, St Michel and Luxembourg stations, for example) to CDG and ORY airports.
The two connect at the ""Les Halles" station in central Paris.
See the RATP site for more details.
Maps
Overview of IPGP and the OBS facility and the RER A connection between them

Connection IPGP - Gare de Lyon RER A (regional train) 
Connections OBS Facility - Noisy Champs RER A

IPGP and its surrounding region (Notre Dame, the Pantheon, the Luxembourg gardens, the Place des Vosges...)

And, finally, an overview of the restaurant, hotels, and some metro/RER stations that might be useful for connections:

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