Dwarvenholme

A massive set of interlocked and interlinked caverns, this network of large dissolution caves was meticulously carved and crafted into housing, manses, manors, fortresses and leisure areas. Dwarvenholme is the traditional birthplace of Tellus' Dwarves, and while "shy" is not a term one would normally ascribe to them, Dwarves are (also traditionally) incredibly wary of outsiders.
So, while there are always exceptions, for an outsider to get into Dwarvenholme is a heroic feat, in and of itself...if only in red tape, paperwork, and government enforced waiting periods.

Geography

The large mansions and domiciles have been built inside a network of dissolution caves that were left behind as massive limestone deposits dissolved over the course of millions of years. It is located under and within the vast range of mountains covering the northern pole of the planet.
The extent of the caverns has never been fully mapped; some would even say it is impossible to do so. The community ebbs and flows like a tide within the confines of the caverns; moving out of old constructions as newer ones become available. The Dwarves themselves are an organism, that lives within and in symbiosis with, the mountains of the far north.

Ecosystem

There is a freshwater river running right through the middle of the giant city. Insects and various fungi and molds have some purchase, but the ingenious air-exchangers the dwarves fashioned long ago keep them to a minimum. The dwarves cultivate various mosses and mushrooms for sustenance, and animal husbandry is not uncommon. Families grow their own vegetarian sustenance in multi tiered gardens that are watered by clever aquaduct systems and lit by bioluminescent mosses and lichen. Children play in playgrounds and climb through tunnel systems made especially for them to play within. Elderly dwarves lounge in public parks playing an ancient game with the unlikely name of Chess with any and all comers. All strata and subclass of dwarven social structure has an enormous impact on the entire mountain range, starting at the most subliminal levels. The dwarves know this, and try to limit it.

Localized Phenomena

There are a variety of bioluminescent mosses and lichen that has been cultivated across the ceiling of the massive caverns. The different colored mosses give off different wavelengths of light, and hold varying degrees of moisture, throughout different parts of the caverns, causing localized weather patterns and a variety of microclimates.
There are also caverns evoking innocent crystalline wonder, and chalk patterned marble, polished to a mirror sheen by sand and running water, all of it bathed in ultraviolet light. There are wonders of every sort within the underground world Dwarvenholme encompasses.

Climate

It is always twilight, lit by the various sources of illumination within the city. It is always 72°, with a relative humidity that's just right for most carbon based, bipedal life forms. There is the right O₂ level for our particular carbon based life forms, but not so much as to immolate the entire mega complex.

Fauna & Flora

Bioluminescent moss and fungus abound, as do swine and goats who have evolved large eyes and ears. There are farmed spiders, house spiders, pet spiders, food spiders, spider gumbo, spider soup, spider gazpacho, silk spiders, toy spiders...there are a lot of spiders everywhere!

Natural Resources

There is a wealth of fish in the river, trout and salmon washed down from above (with a little mechanical assistance from the Dwarves ), and they grow a plethora of medicinal herbs and spices in specialized Dwarven Light Houses spread throughout the megastructures of Dwarvenholme.

History

The dwarves, unlike the rest of the entire world of Tellus, have always made their homes underground, according to their folklore, and thus they were entirely unscathed during the time of and just after the Impact that wiped out so much life on the planet.
According to the Dwarves, their god Moradin tells them that they were born of the ground and under it, completely seperately from Humanity and Elvendom. Also according to the Dwarves, Moradin literally lives and works among them, and is known to each and every one of them.

Tourism

Tourism is strictly prohibited within the inner city. Non-artisan working people and laborers of all ethnicities are always welcome.
There are...loopholes.