They built many famed halls including the Lonely Mountain , Belegost, Nogrod, Khazad-dûm, the Halls of Thranduil, and Menegroth. The Dwarves also re-forged the Great Gate of Minas Tirith and rebuilt the walls of the Hornburg after the War of the Ring.
Their cities appeared to be constructed just under mountains or mountain ranges. Dwarven miners would excavate into the mountains to create an entrance, and then dig through and under the mountain to create the groundwork for their cities. Dwarven cities were very expansive, reaching the far depths of the earth. Dwarves continued to mine in their cities to expand them and discover more resources like precious metals and minerals.
Dwarven cities ran throughout mountains and mountain ranges, stretched up, down and side-to-side in the massive caverns beneath the surface, but it was largely unknown how cities were structured and sectioned off. In Khazad-dûm, there was a section of the city known as the Chamber of Mazarbul, the Chamber of Records. There were also sections of the city mentioned in the Book of Mazarbul such as the "First Hall," "Second Hall," "Third Deep," "Twenty-first Hall" and the "North end."
One stronghold, Erebor (located in the Lonely Mountains), gained its wealth from precious gems hewn from rock and in "great seams of gold running like rivers through stone."
A name for where the Dwarves' were located was Phurunargian, which meant Dwarf-delving in the Common Tongue.
