I recently taught a lesson on the geographic use of "the".  I was unfortunately unable to find a good model text on the geographic "the" on Youtube, and in the time I had to prep for this class, I didn't have time to create one.  So I resorted to just finding videos that explained the grammar.  I played parts of these videos for my class, and asked them to take note of when to use the article "the" with geographic features.

If I ever teach this lesson again, I will try to find time to make a better model text.  But for now, this is what I have.

Article THE with geographical Names - English Club