If you’ve ventured out into Maltese countryside over the years, you’re bound to have come across one of these structures. And if like us, you’ve stared at them, wondering what in the heck they are, we’ve gotchya covered!

This structure is what is known locally as is-salib tad-dejma and was an integral part of many of Malta and Gozo’s towns and villages, playing an important role in the islands’ defense during the Middle Ages. Yup, they’re THAT old.

“As attacks by Ottoman pirates climaxed in those days, the locals decided to set up their own militia. A group of local militia would stand guard in coastal towers,” Maltese Islands Weather share on Facebook, captioning a photo taken by Kappa Vision. “Whenever an enemy galleon was spotted, they would raise alarm and send signals by means of fire (at night) and smoke (by day) to town and village centers. The dejma would then meet by their respective cross ready to intercept the enemy.”