How to solve Hidden Treasure Map Piece 7 in Crimson Desert

Crimson Desert's treasure maps are some of the most devious in any game I've played. Usually, the location you're looking for isn't too far from where you found the clue, but that's not the case here. Hidden Treasure Map Piece 7, which you can pick up from the model castle on the east side of Hernand, is a great example.

While it's likely the first treasure map you'll find, Piece 7 sends you across the entirety of Pywel to find its hidden loot. So don't waste your time running around Hernand for an hour like I did...