Reminds me of the Prora, a weird Nazi hotel compound on the Baltic Sea that was never finished: http://www.amusingplanet.com/2013/01/the-10000-bedroom-nazi-...
Interesting that kraft is analogous to both strength and skill in German. Similarly in old Norse it's both strength and virtue. In English craft is defined as skill, i.e. in making things, yet Northwestern European languages place an emphasis on strength. I wonder if it's because as the language developed it was a time when making things required more strength than mental discipline/skill, such as lifting logs and stone for constructing shelter, roads, retaining walls etc.
"Kraft" can have a spiritual meaning of sorts (vitalize) though. "Kraft schöpfen" is often used to sort of mean gather your thoughts and get revitalized. That's how it's used in KdF. I guess "mental strength" fits most closely in the KdF example.
There's also an old-ish word "Geisteskraft" which means something like mental strength. However it does have a different connotation than skill.
I stand corrected. Based on a quick search, what I gather is that kraft tends to be used (in conjunction with other words) to define forms of force.
Thanks for taking the time to explain in-depth.