The Caravan City of Azul is a d20 System scenario for characters of any level. Part of AEG's Adventure Keep line of short, cheap modules in half-sized format (4-1/4"x11"), it is intended to be run as a single session. From the back cover:

You can scarcely credit what your senses tell you. You see, spread out for hundreds of yards on either side of the main road, a huge, sprawling camp bustling with people. It appears to be a village, except that no maps tell of any settlement for miles around, and besides, villagers don't usually live in weather-beaten tents made of stitched hide. You hear a lute being strummed, a high, sweet voice singing, and an unusually clear ring of hammer against anvil — all of this cutting through the braying of animals being herded toward the long grass outside the camp. A rich scent of cooking food, unlike anything you have smelled before, wafts toward you on the breeze. Then, suddenly and without cause, a burst of bright color lights up the sky, accompanied by a piercing, gleeful cackle.

What is this place? Who are these people?

As you reach the outskirts of the camp, a burly guard with a sharp longsword dangling at his side steps in front of you. He holds up his hand and looks you up and down. Then he smiles, but there is a flinty look in his eye. "Welcome to Azul," he says. "We have two rules here: stay out of trouble, and don't close your purse strings too tightly. Follow them, and you'll have a fine time."