This is a seamless cylindrical panorama of an island at daylight. It's assembled from many separate photographs covering a full 360° circle, which were later digitally processed to remove any seams between them.
Used as a spherical environment and/or reflection map it will bring a new dimension of realism to your rendering.
Tip: use a ground plane with an opacity map fading to transparent over distance in order to receive a seamless flow into this background image. MAX users may use it as a fog texture map.