There is only one file type that uses the .OVL extension:
Rollercoaster Tycoon 3 Data File
Game archive used by Rollercoaster Tycoon 3, a roller coaster creation video game; stores various types of game data, including 3D models, 2D game graphics, sounds, and layout information for the user interface; used as a game data container.
|Atari RollerCoaster Tycoon 3 — Discontinued||Paid|
Updated: November 15, 2011