This great cutaway originally comes from a July 5, 1947 Saturday Evening Post ad for Armstrong’s Industrial Insulation. For an extra-sized view, click here and then click a second time on the magnifying glass.
The ad says, in part:
When you look behind the scenes, a modern hotel is an astounding place. Few guests appreciate that their comfort demands such a complex and highly mechanized institution. The men (1) who ordered ice probably don’t know that there’s a complete ice-making plant (12) hidden away in the basement. The dancers in the ballroom (5) don’t stop to think what it takes to provide air conditioning (11). Touch a spigot (2) and ice water spurts out. Turn a valve (4) and heat is waiting. Heat and cold flow through the hotel like lifeblood in its veins. Insulation on the pipes makes it economically possible to put heat and cold where they are needed.
Cutaways don’t get any better than this one. I’m trying to be an upright and honest Web citizen, but I cannot find the attribution for this photo. Here is the original source.