Middangeard

Middangeard is an anomaly, one which UNSC analysts have trouble reconsiling with established scientific fact. Upon its discovery in 2513, initial reports indicated that the planet was already occupied, with satellite imagery showing sprawling cities and towns dotted across the planets surface. Though these would prove to be abandoned, the planet was deemed suitable for colonisation. Cursory investigations were made on the suitability of disclosing such a find to the public, and the potential risk of tourist damage, but the destruction of Harvest meant that colonisation was put on hold as the UNSC brought its full military might to defend human colonies. A small xenoarchaeological outpost was set up, and after the war interest in colonising the planet increased again.

Prehistory
Exactly who build the Middangeard ruins is a mystery. They were certainly not built by the Forerunners - they predate the early Forerunner civilisation by more than thirty thousand years, and are nowhere near as technologically or even architecturally sophisticated. Xenoarchaeologists are still poring over the ruins, cataloguing and studying all personal items they can find in order to learn whatever can be gleaned about their makers. What is known is that their scientific level was at approximately the equivalent of the Industrial Revolution. For whatever reason, the species that inhabited Middangeard disappeared approximately 250,000 years ago, leaving behind their entire civilisation virtually intact. Much of it is estimated to be lost forever - materials such as wood would have decomposed long ago, exempting unusually well-preserved specimens, though much of their "grand" architecture remains, constructed of stone or primitive concrete. Exactly what happened to them remains unknown - a series of craters in the northern hemisphere leads some to conclude that the civilisation was destroyed by a "nuclear winter" from the hits. Biologists have speculated that they may have been wiped out by a planet-wide supervirus. Some fringe scientists claim that the civilisation may have simply advanced to the point where they left their home world behind, without bothering to posit what may have forced an entire species to leave its home world en mass. So far, no grave sites have yet been found - their culture seems to have preferred ritual cremation over burial, leaving little behind for study.

Quotes

 * "It's haunting. All the infrastructure is still there, like the day it was left - the streets, the buildings, even the rooms still have some personal artefacts in them. Its an archaeologists dream, studying a dead civilisation preserved so well - now if only we could find out what happened to them."
 * "The architecture is strange. One moment you're looking at what looks suspiciously like Heian period Japanese rooftops, next thing you see are Classical Roman columns, and then medieval embrasures, merlons and buttresses. And they're all made of stone or a type of concrete - these things were built to last."
 * "What we're left with is just the pinnacle of whatever civilisation lived here. Anything made of wood or other organic compounds would have rotted away long ago, so we have little left of the normal, everyday life of their builders."