The conference will take place in Sciences II and III building. The address is 30 quai Ernest Ansermet (see map below) in Auditorium A100 Sciences II.
The entrance of the buidling can be seen in the two pictures below. The Auditorium is on the ground floor, just a few steps from the entrance shown here.
September in Geneva is usually beautiful, with quite hot sunny days, but already fresh evenings and nights.
Check the meteo on meteoblue.