Historical maps are excellent if your story takes place in a city. You can know exactly how the streets ran, how many buildings on the street, etc. Google Earth does the same thing for modern stories.

And I like getting blueprints to buildings similar to key buildings in my stories, so I know where all the rooms are in relationship to each other.

The most unique worldbuilding exercise I ever did was trying to describe an important river. I'm crap at distances. So I drove around crossing rivers in NY until I found one that was the appropriate width and depth of the one I imagined, and then found out how wide and deep the actual river was.