From Halopedia, the Halo wiki
Sector 0 is one of the sectors in the city of New Mombasa, Kenya, Earth, located on the northern side of the Mombasa island. The Kikowani Metro Station was located here.
A map of the sectors in New Mombasa.
The sector's number shown on a wall.
A Traxus building in Sector 0.
The entrance to Kikowani Station.