Yamen Fort truly is off the beaten path
Doumen is truly far off the beaten path, even for domestic Chinese tourists. You will most likely be the only visitor at any given time inside the fort. It's neat to have the entire fort to yourself and imagine you are waiting for enemy ships to pass by.
Doumen can be done as a day trip from Zhuhai or even Macau. You can see the fort from the river if you take a ferry to Xinhui or beyond.