Located in the Vespucian Arm, Sector 1, Sub-Sectors G, K, and L. With most of it in Sub-Sector K.
When the First-In Scouts came to this area a few hundred years ago, no intelligent beings were found.
A few small animals of many types. Nothing larger than a small deer. No large birds. No large carnivores.
Each planet had large stone cities. Obvious signs of laser cutting tools. No electricity other than lightning.
The first archaeology teams found no burials of the vanished peoples that must have made these edifices.
No utensils, no food storage buildings. The area became boring to archaeology. They left.
Bases here and there, towns sprang up from immigrants. A few inter-system Spaceports, farms near the towns.
But no sign of the original inhabitants.
Something howls out there at night on several of the planets. Noisy brightly lit robotic rovers find nothing.