Charum Hakkor
From Halopedia, the Halo wiki
Charum Hakkor is a planet in an unknown system that once served as the heart of the Human-San'Shyuum Empire. It featured a wealth of Precursor architecture and structures.
Charum Hakkor was the site of the concluding battle of the Human-Forerunner War, and also the location where the Didact and Librarian first met.