What is length scale?

So this week's assignment posed some difficulty for me. I needed to find a structure, on the Penn campus, that demonstrated three different length scales. I thought about this for days on end, but nothing really came to mind or struck me with the thought of, "that definitely would work." I guess for me, the problem was what exactly defined a length scale? If I don't know what it means, how can I find an example of one? This is a concept that I struggled with for a while. To be honest, I still don't fully understand it. If a length scale is something that is determined by an individual, and can be custom altered to fit to a specific thing, then how does one define it? I guess what I figured out by the end of this week, though, is that there isn't really a definition for length scale. It varies based on whatever it is being applied to, but that's what makes it so useful. It can be used for whatever you need it to.