This is one of a collection of environment maps shot as full 360º equirectangular, with a high exposure value of up to 14f stops. Included in the set are;

8k (8000 x 4000 pixels) spherical JPEG background
4k (4000 x 2000 pixels) spherical HDR for reflection
Low-res light-map (360 x 180 pixels) spherical blurred
Thumbnail JPG (128 x 128 pixels)
sIBL document
Example test render
360º QTVR to help view the panorama