Well, we have two of three of the last installments Identified: UI 57 is the Matterhorn at Disneyworld (unlike the real Matterhorn in Switzerland), and UI 56 is a railroad bridge over Lake Britton in California. The bridge is more famous for appearing in a movie set in Oregon: fictional Castle Rock, Oregon, to be precise. This is the trestle where Gordy and Vern nearly perish under the wheels of a train in Stand By Me.
UI 55, however, is still Unidentified! OK, OK, I made this one way too hard -- although a good guess was offered on the comments for another entry (it's not Brady's Bend). The only way anyone will get this is if they're into whitewater rafting, kayaking, or canoeing. Doo de doo de doo...and now for the new puzzler!
Where are we? Rot-13 your guesses, please!