You can use this same technique to view glasses-less 3D (stereoscopic) images. It's also fairly easy to create your own. Take two photos but offset the camera lens by approximately eye-width. Open the image editor of your choice and place the images side-by-side. View the composite image cross-eyed and you are now viewing a 3D scene.

Also worth noting there are 2 versions of this kind of cross-eyed focus depending on whether your eyes are focusing on a point in front of or behind the actual image. This determines which side the left and right eye images should go on in the composite. I find it easier to focus on a point in front of the images but IME most examples online are for focusing on a point behind the image.