If you’re into this genre checkout this one made by an Indie Argentinian dev https://store.steampowered.com/app/1345370/Promesa/

Another famous one is called Proteus https://store.steampowered.com/app/219680/Proteus/

A recent one that many love is called A Short Hike https://store.steampowered.com/app/1055540/A_Short_Hike/

A Short Hike is a great game and another one of my favorites, but I wouldn't call it a walking simulator since there are challenges. I'd call it a parkour-inspired game.

Many walking simulators are very linear and railroad you into doing specific things and going to specific places. An example of this is Firewatch.

IMO the defining feature of a walking simulator is that they have no actual mechanics. Many games tell stories through exploration, finding audiologs etc., but they usually have other gameplay mechanics like shooting, puzzles, survival, whatever. Most gamers see gameplay as pretty essential to the medium.

A walking simulator strips all that away and leaves only the most basic possible mechanic: walking around. Most don't even let you interact with the world or with characters. I think this precludes this game from being a 'sandbox' as the article suggests.

Incidentally, I happen to have made one for an event called Gamma 256, which took place 13 years ago today: http://doomlaser.com/trekking-across-the-northeast-for-gamma...

Of course, in 2007 the genre didn't yet have a name.

Possibly qualifying - a game called Everything: https://store.steampowered.com/app/582270/Everything/