Schloss-Hotel, Heidelberg, "Bird Cage"
From chapter 2, p. 28:
"This hotel had a feature which was a decided novelty, and one which might be adopted with advantage by any house which is perched in a commanding situation. This feature may be described as a series of glass-enclosed parlors clinging to the outside of the house, one against each and every bed-chamber and drawing-room. They are like long, narrow, high-ceiled bird-cages hung against the building. My room was a corner room, and had two of these things, a north one and a west one."