From Halopedia, the Halo wiki
In Halo: Reach, some maps contain special locations that appear on the player's heads-up display when they reach certain areas. Finding one of these special areas in Halo: The Master Chief Collection will unlock the Confused Callouts achievement.
On Powerhouse, if the player drops down the waterfall to one spot on the rocks where they can't be killed by the barriers then the location next to the radar will say "Vaya con Dios!" which means "Go with God."
On Condemned, if the player manages to get out of the map, on the outside there will be a small portion where the location reads "Space".
On High Noon, if the player go to the center of the map, in the "Construct of mordia", in the lowest part of the structure there will be a text saying "In memory of Peter Marks", who was the designer and creator of the original map, Hang 'em High, who died of cancer in 2009.
On Boardwalk, the triangular balcony beneath the metal shade is referred to as "Make Out Point".