This city was surrounded by high fortified walls, and contained a place of assembly for the people and rude habitations, the remains of which are still visible. There is also still to be seen a conical or bee-hive-like structure, commonly called the Treasury of Atreus. This cone is formed by overlapping stones, curving gradually until they meet at the top of the vault, which is capped by a large block. The doorway by which it is entered is composed of slanting jambs of stone, sustaining a massive lintel. This lintel is relieved from direct weight above by a triangular opening, obtained by a similar process of corbelling. The Cyclopean remains are of interest to architects chiefly on account of this system of corbelled vaulting employed in their construction, which would never have been adopted had their builders been acquainted with the voussoir principle. Dr. Schliemann has recently excavated the Acropolis of Mycenæ, and found there many interesting objects of gold and pottery. Bronze nails with flat heads have also been found within the Treasury of Atreus, which were evidently used to attach copper plates with which the interior was lined. Pausanias speaks of a similar treasury belonging to King Minyas, at Orchomenos, and other remains of the same description have been discovered in different parts of the Morea, bearing a resemblance to the ruined cities of Etruria. In fact, the various tumuli found in Western Europe, Sardinia, Sicily, Greece, and Asia are all of the same type, and were a form commonly adopted by the ancient nations. When we come to the epoch preceding Roman architecture, we will examine the character of Etruscan buildings, which were similar in many respects to the works of the Pelasgi; at present the subject of most interest is that of the great century of Greek art, for it marks the transition from Crude Art, to which belongs all that has preceded, to Fine Art, in which the Greeks excelled.