Lock up your landmarks

from here and here (source article)

I actually don't know what kind of theft prevention measures you can use here. What are you going to do, chain it to a tree? Anyone with the capability to move a bridge also has the capability to eliminate any restraining mechanism you might employ like a lock or chain. This kind of threat is beyond traditional preventative measures, but detective measures like motion sensors or surveillance cameras might do the trick. The only issue is that who anticipates this kind of threat in the first place when they formulate their threat model?