Coral
From Halopedia, the Halo wiki
Coral is a human planet. In I Love Bees, it is said to be 42 lightyears from Earth. This may simply be a reference to 4orty2wo Entertainment, the company who produced I Love Bees, but others have theorized that this refers to the star HD 69830, which happens to be exactly 42 lightyears away in the constellation Puppis.
As described in Conversations from the Universe, a mining operation uncovered the tip of a Forerunner installation. The miners used explosives to evaporate a depth of 30 meters, except for the tip of the installation, which wasn't even scorched. Archaeologists funded by ONI were able to dig out about eighty meters of the complex, which seems to be much bigger. The complex has been described as made from metalic crystal, symmetrical to a near-atomic scale, yet adorned with decorative artistic motifs.
According to I Love Bees, the planet has since been glassed by the Covenant. But while I Love Bees was before many plot twists in the story line, Coral may not have been glassed. According to Conversations from the Universe the planet held a Forerunner artifact; therefore, the Covenant would likely never glass the whole planet. This would make the planet just like Reach in terms of destruction.
NOTE: The Halo novel Ghosts of Onyx had a working title of "Ghosts of Coral". This led to a great deal of speculation about the planet, none of which can be confirmed.
