Montezuma Well (Yavapai: ʼHakthkyayva), a detached unit of Montezuma Castle National Monument, is a natural limestone sinkhole near the town of Lake Montezuma, Arizona, US, through which some 1,500,000 US gallons (5,700,000 L; 1,200,000 imp gal) of water emerge each day from an underground spring. It is located about 11 miles (18 km) northeast of Montezuma Castle.