Finally, add an adverbial phrase to explain how long the site has been fortified. Click here to get to a fascinating analogy about modifiers. You'll be glad you made the trip. In some cases, main clauses are split when free modififers come between subject and predicate. Here are other examples of sentences broken out to show levels of subordination.
Modifiers provide details or additional explanations of statements made in the main clause.
The closer the camera is moved, however, the more it can discern the patterns of individual columns and the stances and dress of the figures represented on the friezes. So to illustrate levels of subordination is to provide graphic depiction of how modifiers are related to the main clause and to one another.