When Perseus discovered the fountain, he assured the most basic commodity for the new city: water. This infinite treasure, the Perseia fountain, still springs nowadays and supplies the modern settlement. It was connected to the citadel through an underground reservoir that was manufactured in the 13th century BCE and could be accessed by a narrow, underground passage. It constitutes an architectural marvel and is situated at the north-eastern side of the acropolis; its purpose was to provide water to the Mycenaeans, who were forced to confine themselves within the Cyclopean fortification if they were under siege. The fountain is 360 m away from the citadel, to the north of the wall and 13 m above it. Nonetheless, the Mycenaeans had found a way to transfer water through aqueducts.
The wise design and know-how of the water supply system of Mycenae evokes admiration even today, 33 centuries later. The entrance of the reservoir was made from cast material. A downhill staircase of 16 steps leads to a second staircase of 20 steps situated to the east, having a direction parallel to the wall. This underground, escalated tunnel leads to a third staircase of 54 steps that lead to the reservoir. The reservoir's vault is pointed, covered with special mortar and with a depth of 5 m. At the top, a vertical tank was constructed, surrounded by scarcely placed blocks that functioned as filters. This is where the underground pipeline coming from the fountains ended. The location of the palace at the hills, the Cyclopean masonry, and the secured water supply transformed the Mycenaean palace to an unconquerable fort.