Approximate location — plotted from published sources, not a site visit, and not a guarantee of access.
Detached unit of Montezuma Castle National Monument: a limestone sinkhole ~370–386 ft across continuously fed by ~1.5 million gallons of spring water per day. High dissolved CO₂ excludes fish but supports several endemic aquatic species; Sinagua cliff dwellings, pithouses, and a prehistoric irrigation canal ring the rim. Free to enter — a compact geology + cultural oasis in the Verde Valley.