Castles at sea are a pray on which many pirates are aiming and this one is no exceptions. Pirate sailing ships can be seen at the horizon and the might eye might catch them in time to defend. This will give the signal to all Romans to wake up, turn the stones into flash and fight again to defend what is theirs.
My creation has been done using Adobe Photoshop Elements and the used images were from Pixabay.com "Free for commercial use. No attribution required."
Sailor spyglass man ship lookout
The main image is from @shaka.
Hope you like the interpretation if the defended castle.