From Halopedia, the Halo wiki
Caracas was a city on Sigma Octanus IV, named for the capital city of Venezuela on Earth.
Battle of Sigma Octanus IV
The city was destroyed during the Battle of Sigma Octanus IV in July 2552; it was either glassed by the Covenant or destroyed by the UNSC to deny anything of interest to the former. Vice Admiral Michael Stanforth estimated that it would take up to a dozen years to repair the city.