Dear Esther (2012) began as a mod for Half-Life 2: Episode Two (2007) back in 2008. It received almost universal praise for its design and atmosphere, sparking an overhaul that improved the graphics and tweaked the level layouts. The project continued to grow until early 2012 when the completed version was released.
In the game you can find objects that exist in real-life, like the Callanish Stone Circle.