Limestone has been used as a building material for centuries
Limestone has been used as a building material in Malta and Gozo for centuries. This applies equally to churches and cathedrals as well as to private houses. Even nowadays, limestone is still number 1 for new buildings. That is why the many places on Malta and Gozo seem "as if from a single source".
The limestone is mined in huge quarries, milled into a cuboid shape on site and transported by truck. There is even an open-air museum in Malta in a disused quarry dedicated to limestone: limestoneheritage.com