The Tarrasque Market

Describe a bustling market settlement in your world. What can I find for sale?
The shell of a dead Tarrasque (larger than any ever written about) creates a pavillion for a market that specializes in trade with the Underdark. The rear of the shell is embedded in the base of a mountain, under which a massive tunnel to the Underdark leads. The Tarrasque appears to have burrowed out from under the mountain and died at that spot.
The Tarrasque Market is located in a break in the Terras. The Terras are a ridge of mountains that runs southeast from the Cataclysmites in South Krahnis. They are individual mountains strung together and they have three considerable breaks or valleys between them until they spread to become more isolated hills. At the head of the shell, there is level ground that connects through the mountain break. Fortress walls were built here and passage through or down into the market requires a toll. From the head end, there are ramps running down into the sunken market.
The market was founded long ago by a drow, Azarian Bru'Zhan. Prior to that it was an outpost of the surface world guarding the entrance. Later it became an outpost of the races beneath Urth. It was really just an excuse for one of them to charge a toll for use of such an easy pass through the mountain and under it. The market started around the need to feed and supply the military stationed there. The location suffered some large attacks from the tunnels, occasionally forcing it to be abandoned until someone thought up the idea again. But Bru'Zhan founding the market and placing under the influence and province of the drow stopped attacks from any creature intelligent enough to fear the Drow. Of course, Bru'Zhan's Drow were quite worldly and often ventured to the surface. The darkness of their culture was not as terrible as those Drow dedicated to Lolth. There are no other open markets to the deep in South Krahnis. The Mastiphe Impasse is directly connected to the Underdark, but there have never been settlements that were stable enough to survive a year. This market has operated for a few decades now, and a few more years before that when it was a secret few had heard of.
Today, the market is quite refined in operation. Guard towers are built on the top of the shell. Gutters surround the edge of the shell funneling rainwaters down to supply the market below. Metal catwalks weave on the underside of the shell, standing 30-50 feet above the market floor. The sides once had some gaps, but they have been dug out and covered in glass to let more light but only onto the edges of the pavilion where it is easily avoided by light-sensitive creatures. Metal chimneys rise along the edges and a few actually pierce through the shell. Smoke pours from some of them at all times.
The market once was nothing but tents from merchants who came and left, but now contains actual buildings of brick and mortar. Although most have only fabric roofs as they are protected under the shell. Some merchants live here year-round now.
The more civilized of the upper regions of the Underdark bring goods here and buy things that cannot make down below. Foods, vegetables, fruits, baked goods, meats, spices are the most popular to customers from the Underdark as the sunlit world has greater variety in this area. From the deep come a bewildering assortment of fungi, roots, moss, lichen, and unusual plants. Ales, wines, beer, ciders, vinegars, and waters from both sides are plentiful.
Materials from the Underdark, including ones that are considered dangerous or even evil are quietly traded out of sight here. Spellcasters looking for odd components or materials for enchantments are always here. Craftsmen from above and below peddle wares mundane and unusual. And services can be bought here. If you need to ask what kind, then there aren't any you'd be comfortable with. Magic from both worlds is traded here.
An assortment of races is here, including ones that many could not identify. Animosities must be left outside the shell. Forces keep the calm and they are impressive. Usually, there are some large creatures patrolling, their heads easily above the walls of the buildings.

Type

Trade post