Urborg is a Sphere in the independent quarters. It is a primarily jungle-dominated Sphere, almost entirely covered by a canopy of greenery. The entire sphere is filled to the brim with diverse and enormous plant life, and it's rumored that some of the flora are more active than seen anywhere else in Aurora. The animal savagery makes it too difficult to settle in dense jungle, but smaller islands are inhabited by hardy humanoids that make great use of the plant life.
Like most spheres in the independent quarters, it holds an untold amount of old secrets and wealth in its darker corners. However, it is prohibitively dangerous even for skilled adventurers. The main reason neither Bulwark nor Waether have tried to settle it is due to the amount of forces it would take to overrun the opposition lying in the jungles, and even then it may require irreparably damaging the wilderness.