From the Gare de Lyon station take Ligne R to Melun with a Transilien ticket (direction Montereau or Montargis; direction Laroche-Migennes is also possible but verify that the train stops at Melun). The journey normally takes 35 minutes.
The Ligne R trains leave from Level 0 in Hall 1. If you arrive at the Gare de Lyon by RER or metro, you will have to walk up a lot of stairs. Normally, the Ligne R trains depart from platforms with the letters J to N, but occasionally they leave from the TGV platforms A to H. Check on the screens to find the platform letter and departure time. You can buy tickets from the Transilien machines.
The conference centre is 3 kilometres from the railway station.
The best option is to take a taxi. Taxis should be easy to find at the railway station and cost around 11€. Direct the taxi to Le Rocheton (the intersection of the Rue du Rocheton et the Rue du Stade).
Please see the conference center's web page.
Take the ligne R train to the Bois-le-Roi station (bikes are allowed on the train outside of peak hours). Leave the station by following the platform in the direction of the train to a ramp. At the bottom of the ramp, turn right and then left into Avenue Paul Doumer (or go via the mairie). Turn left just before the bridge over the Seine into Quai de la Ruelle which goes along the chemin du halage (a trail once used by horses to pull barges) which is covered in bitumen. Go beyond the last houses of Boie-le-Roi and, further along, turn left onto Chemin de Brolles. This path arrives directly at Le Rocheton after going up a bit steeply through a forest on a trail that is often quite rough but not very long. This route has few cars and some very pretty scenery.
For the brave and fit the GPS coordinates of the centre are 48.506787558850135, 2.6634714136486104 and a possible route is described below. Please do not attempt to walk after dark or if there is heavy rain. The walk takes at least 40 minutes.
An alternative to the Impasse du Clocher is to take the Rue de la Forêt right after leaving Avenue Jean Cocteau. This street turns to the right to give a right angle whose hypotenuse is the Impasse du Clocher.
Some words of advice: do not take the pedestrian routes via the N6 which has heavy traffic and often no proper footpath. We do not want to lose any attendees! Some sites suggest to take a bus from Melun station to Livry-Sur-Seine. While this bus does operate on Sunday, and Livry is not far from La Rochette as the bird flies, the only way to cross the Seine from Livry is by swimming...
If you have any problems please contact Tim, Thérèse, or Marc by telephone or mail. The phone number of the conference center is 01 64 37 12 32 but it is unlikely that the reception will be staffed after hours.