In StarCraft 2, some maps have built in gizmos that affect game play. These are destructible rocks, line of sight blockers (like tall grass or smoke vents), and Xel'Naga Towers.
The destructible rocks can block expansions, or vulnerable passageways to the enemies base. Destructible rocks are Armored, and have 2000 health.
Ground units can not see through line of sight blockers, but can pass through them.
The Xel'Naga Tower is a neutral building, that if a player moves a ground unit nearby, it gives a huge line of sight radius around it to the player and his allies.
All three of these gizmos are present on all known multiplayer maps.