Jixal

Jixal (/dᴣixal/, from Terran: j’Xara;“Place ofTopaz”), otherwise known as the Topaz City, is a city-state on the Elemental Plane of Earth encompassing the entirety of the interior of a "planetary" cavern, the Jixal vault.

One of only three members of the Jixal Planetary System, Jixal's relative isolation has forced its large population to greatly advance intra-planar travel. Jixal is known as the origin of the first cavernship to travel faster than the speed of light.

Geography
Although the majority of the buildings in Jixal are the rock-cut structures typical of Djot-ten, the skyline is dominated by a series of structures known as the [name]. These buildings, which are several dozen stories taller than the surrounding city, are hewn from pure gemstones. The most well-known (as well as the tallest) of these is Xara, which is composed of topaz and is the namesake for both the city and its epithet.