The Mediterranean island of Malta is home to a puzzling archaeological site that consists of a collection of pairs of parallel lines, or grooves, carved into the rock of the ground. These grooves, thought to be at least a few thousand years old, can be quite long, and they seem to connect various locations on the island. There are several theories that attempt to explain the origin of the grooves. One theory suggests that the grooves were carved as irrigation channels to carry water. Ancient societies, like those on Malta, depended heavily on agriculture, and agriculture requires having enough water for crops to grow. The grooves are large enough to carry a significant volume of water, and given that Malta has limited freshwater resources, it may be that the grooves served the purpose of irrigation. Another view is that the grooves were made by wheeled vehicles, such as carts used to transport objects. If carts traveled over the same path repeatedly, their wheels could have created noticeable grooves in the rock. Similar-looking tracks have been found at other locations around the world, but the Maltese grooves stand out because they are much deeper. This may be because the rock in Malta consists mostly of soft limestone, which can easily be worn away, especially when wet. Given the softness of the Maltese limestone, it is possible that carts left the deep grooves. Finally, the Maltese grooves may have been created to serve some astronomical purpose. Many ancient cultures closely studied the planets and stars, and some of those cultures carved marks or grooves into rock that appear to have been used to make astronomical observations. Some ancient stone grooves found elsewhere in Europe have been shown to have connections to the movements of the Sun and planets. So the Maltese grooves may also have been made by ancient astronomers who used them to predict the locations of the Sun and planets.