In 2005, a 44-year-old truck mechanic named Roger Castillo was walking his dog along the Guadalupe River. The San Jose native was no stranger to the river, having fished it as a boy, and remaining a citizen scientist of the river into adulthood. But on this particular walk, when his dog started poking around the side of the embankment, Castillo saw something nobody had ever seen in the river: the bones of a Columbian mammoth.

Castillo alerted a San Jose State University geologist, along with the owners of the property. With the help of scientists from UC Berkeley’s Museum of Paleontology, the protrusions from the river bank were determined to be the tusks of a 12,500-year-old juvenile Columbian mammoth (Mammuthus columbi), and the most complete remains of a mammoth ever found in Santa Clara county.

The mammoth remains were excavated and are now part of an exhibit at the Children’s Discovery Museum of San Jose. Along the bike path, just north of the San Jose Mineta International Airport, the site of the discovery is marked by an 11-foot-tall bent pipe sculpture of a Columbian mammoth. Designed by Freyja Bardell and Brian Howe of Greenmeme, it weighs nearly 12,000 pounds.