If you needed to move all of these buildings, you could group them first.
Suppose you've made a map. You've got several buildings clustered together. It looks perfect. But oops… The cluster of buildings is on the wrong street. You need to move all the buildings down one block. You could select each one and move it down separately. But does that sound efficient?
With Visio, you can group the buildings so that the cluster stays bound together, and you move them all at once. Now that sounds efficient.