Venue
The conference takes place in the Campus im Neuenheimer Feld, in the Golden Box (Physikalisches Institut INF 226). See more details on the venue, the hotels and the restaurant where the conference dinner takes place on this map. As you can see, one of the suggested hotels is at walking distance (10-15 min) from the venue. The closest tramway and bus stop is "Neuenheim Bunsengymnasium". Bus lines 29 and 31 and tramway lines 21 and 24 stop there. If you want to use public transport, consult the page vrn.de to get schedules and more precise information.
Arrival to Heidelberg
Mannheim (15 Min from Heidelberg) is very well connected with other big European cities in the high-speed network (TGV, ICE, ...), which makes a train-travel an option even if you come from outside Germany (e.g. it is in occasions, as fast as 3:25 hrs travel from Paris to Heidelberg). If you wish (or have) to arrive by plane, the nearest big airports are Frankfurt and Stuttgart.
Hotels
The hotels that were recommended in the e-mail you received, need you to give a code. You should use the contact details given to you; the four hotels confirmed to take reservations via e-mail. If you plan to cover your stay, the roughly approximated price is 100 €/night. Do not give on the web pages of the hotels your credit card / bank account details.