From Halopedia, the Halo wiki
Tourist is an achievement in Halo 3: ODST. It is awarded for accessing a Superintendent terminal and downloading the map of New Mombasa to the VISR database. It is worth 5 Gamerscore. This achievement will unlock a Black ODST T-shirt for your Xbox Live avatar on Halo Waypoint.
It is represented by a part of the map of Mombasa, with the outline of the Superintendent's face over the map.