My daughter and I stayed for several nights while attending a conference that was hosted in the downstairs conference room. Being adjacent to the Heidelberg Hauptbahnhof, trains to points of interest such as Speyer and Frankfurt and busses and trams to old town Heidelberg were very convenient. We do recommend requesting a room on the opposite side of the hotel as the train tracks because regular passenger service and accompanying PA announcements are incessant from 0500-2400 and then the freight trains take over. The windows are well insulated for sound, but due to the noise (which is to be expected next to a train station), could not be used for ventilation while wanting to sleep. Also, there is an apparently a switch associated with the windows and the air conditioning. A sign informs the tenant that the windows must be closed for the air conditioning to work, but does not inform the user which handle position (out of three) on the window is "closed," so it took us a while to figure out how to configure the windows to cool the room during the warm sunny days of our stay. The above are not complaints, but intended as observations for future visitors.
Also, be certain to sign up for the hotel chain's "H Rewards" program to get free local bus and tram day passes.