How were the fortification walls of Hattusa constructed?

The fortification walls of Hattusa, the capital of the Hittite Empire, were constructed as a powerful, four-mile circuit surrounding the outer city. These defenses featured the following structural elements:

• Double Walls: The city was protected by a system of double walls equipped with defensive towers.1
• Cyclopean Masonry: The substructure of the walls utilized cyclopean masonry, which consists of large, irregular stone blocks fitted together without the use of mortar.1
• Ramparts and Aprons: These walls were built upon a stone-faced rampart made of earth. This rampart was further reinforced and protected by an additional stone apron wall.1
• Gateways: The city gates were designed with corbeled arches and were flanked by monumental portal sculptures, such as lions or sphinxes.1