They call themselves the Khazâd, but the rest of Middle-earth knows them as Dwarves. They are a unique race throughout the lore of The Lord of the Rings, with their own origin story, writing system, and civilization that is literally carved in stone.
Every story Tolkien wrote included some important character and location of Dwarven origin. The entire story of The Hobbit was about the restoration of a lost Dwarf kingdom, and Khazad-dûm has played a prominent role in The Lord of the Rings books, with this famous location also featured in both Peter Jackson's adaptations and the Amazon series Rings of Power. There are several other Dwarf cities in Middle-earth, and they are equally compelling and mysterious, which is why artists and intellectuals like Celebrimbor and Elrond loved them so much.
7 Belegost
Of course, one of the first real, sprawling cities that was built in Middle-earth was built by the Dwarves. Belegost was located under the Blue Mountains, convenient to the realms of the Sindar Elves. During the First Age, the most prominent of these was Doriath, the realm of King Thingol and Melian the Maia.
The Dwarves of Belegost built the capital city of Doriath, Menegroth, which included the King's throne room and residence. The reward for their hard work was the giant pearl Nimphelos, originally given as a gift to Thingol from Cirdan the Shipwright. The Dwarves of Belegost would make a name for themselves again during the War of the Jewels when they withstood the dragon fire that was deadly to humans.
6 Erebor
It's better known by what it was called in The Hobbit, The Lonely Mountain. The term Erebor was an Elvish one that everyone seemed to use, and it referred to both the mountain and the city within it, and if there was ever a unique name in the tongue of the Khazâd it was hidden and lost to time.
The rise of Erebor as a dominant force in Middle-earth came after the fall of Khazâd-dum. Refugees from the Misty Mountains bolstered the population of both Dale and the Dwarven realm, and it was during this time that King Thráin became the first King Under The Mountain. The dragon Smaug drove the Dwarves out for a generation, but a covert force led by Thrain's descendent Thorin was able to reclaim Erebor and rebuild what was destroyed.
5 Aglarond
Also known as The Glittering Caves, these are described in glowing detail in The Two Towers and are based on a real location. Tolkien wrote in The Letters of J.R.R. Tolkien that they were based on a place called Cheddar Gorge in Somerset, a place of high jagged rock outcroppings, verdant lichens, and the glow of exposed minerals.
Aglarond wasn't exactly a city, but they were inhabited. They were a natural phenomenon that was only developed on a larger scale when Gimli brought some colonists there with the permission of King Elessar at the end of the Third Age. The only humans who knew anything about them during that time were the Rohirrim because the Glittering Caves made up part of their refuge, the Hornburg.
4 Khazad-dûm
Not just the best-known city amongst the Dwarves, but a famous cosmopolitan center that dominated virtually all of Middle-earth for most of the Second Age. It was also known as Moria or Dwarrowdelf, and it was located deep under the Misty Mountains.
Khazad-dûm dates from the Years of the Trees, constructed before there was even a sun and moon, and even before Feanor had made the Silmarils. Dwarf legends say that the first of them, Durin the Deathless, woke at a place called Mount Gundabad just north of the future Mines of Moria.
3 Nogrod
The sister city of Belegost, Nogrod was also located under the Blue Mountains but it was further south and more convenient to the Dwarf Road and the mountain passes that led into Beleriand. It was founded at about the same time as Khazad-dûm and Belegost and was home to two of history's greatest smiths, Gamil Zirak and his most gifted student, Telchar.
Gamil Zirak was famous for his work on the Caves of Menegroth and several of the most impressive treasures in Doriath. The kingdom makes an appearance in The Silmarillion when Eöl, an Elven smith of no small renown, visits the kingdom with his son, Maeglin.
2 Ered Mithrin
The Iron Mountains were a vast range that stretched across most of Middle-earth in the First Age. After the War of Wrath, it was broken like much of the continent, and these vast mountains dwindled into several pieces, one of which was the Grey Mountains. They were also called the Ered Mithrin and were located on the northern borders of Rhovanion.
Similar to the Glittering Caves, this realm had been settled by Dwarves since their earliest history but was not highly developed. It was close to Mount Gundabad where Durin first awoke. The danger of orcs and dragons was what kept the area from being settled on a larger scale until the Third Age.
1 Iron Hills
The Elves called it Emyn Engrin and can be found north of the kingdom of Rhun, making it the most easterly Dwarven kingdom in Middle-earth. The Iron Hills themselves never appear in any of the literature or on-screen adaptations, but their leader Lord Dáin Ironfoot does appear in The Hobbit as one of the leaders of the Five Armies, and after Thorin was killed in said battle he became the new King Under The Mountain.
Most of the refugees from Smaug's attack went east, making the Iron Hills a more prominent Dwarf settlement. After Dáin also became responsible for Erebor, many of his people moved there as well, and the Iron Hills remained a thriving Dwarf realm.