naturalarches.org: A natural bridge is a type of natural arch. In general, a natural bridge is distinguished from other types of natural arches by having one or more of the following attributes:

- a current of water, such as a stream, clearly was a major agent in the formation of the opening (hole)
- a current of water, such as a stream, flows through the opening (hole)
- it is being, or has been, used by man as a bridge supporting a portion of a road
- it has the general appearance of a man-made bridge, e.g., a flat, level top over an arched opening

Hippiepunkpirate's elaboration: Please consider the above criteria before labeling a feature. If the feature you are labeling meets at least one of the above criterion, it should be labeled here (natural bridge). If the feature does not meet at least one of the above criterion, please consider labeling under "natural arch".

Examples:
Delicate Arch in Arches National Park, Utah would be labeled "natural arch".
Sipapu Bridge in Natural Bridges National Monument, Utah would be labeled "natural bridge".

The Colorado Plateau has many world class examples of natural bridges, the most famous being Rainbow Bridge near Lake Powell. Natural Bridges National Monument exhibits three spectacular natural bridges carved out of sandstone.

In the Arizona transition zone exists Tonto Natural Bridge, the largest known travertine bridge in the world.