The Campo del Cielo refers to a group of iron meteorites or to the area where they were found situated on the border between the provinces of Chaco and Santiago del Estero, 620 miles northwest of Buenos Aires, Argentina. The crater field covers an area of 380 acres and contains at least 26 craters, the largest being approximately 110,000 square feet. The craterís age is estimated as 4,000 to 5,000 years. The craters, containing iron masses, were reported in 1576, but were already well known to the aboriginal inhabitants of the area. The craters and the area around contain numerous fragments of an iron meteorite. The total weight of the pieces so far recovered exceeds 100 tons, making the meteorite the heaviest one ever recovered on Earth. The largest fragment, consisting of 37 tons, is the second heaviest single-piece meteorite recovered on Earth.