We loved Volker's place. It is within minutes walking distance of the beautiful old town as well as the castle. The apartment is very charming, and was plenty spacious for the four of us. The kids loved the loft upstairs, their own little hideout. The internet was fast and stable.
The walls may be a bit thin, as we could hear other people at times. But they settled down before we went to bed, so that was not a problem.
Volker, the host, always answered our emails promptly, and was there to greet us when we arrived. Despite the sub-zero temperatures outside, he had a keg of beer tapped, just in case.
We hope to return to Heidelberg, and we'll definitely stay here again. We couldn't have wished for a better experience. Thank you!