There are several hotels in the Heidelberg Old Town within walking distance from the conference venue, such as Hotel Hackteufel, Hotel am Kornmarkt, Hotel am Schloss, and Hotel am Rathaus.
Outside the Old Town, possible lodging options would be Leonardo Hotel City Center (on Bergheimer Straße) or ibis Heidelberg Hauptbahnhof (directly at the Heidelberg main station).
Many other hotels and apartments are within walking distance of the conference venue and spread across the city. These lodging options can be booked e.g. via booking.com or airbnb.com.
As Heidelberg is a popular tourist destination, we strongly recommend that participants book their accommodation as soon as possible.