Longmont Museum

Luke Runyon / KUNC

In the foothills outside Longmont, Colorado, tucked high in a narrow valley, sits an ugly, cement slab. It's the size of a train car and juts out into North St. Vrain Creek, a shallow alpine stream that serves as the city's main drinking water supply.

A tiny sign greets hikers as they pass the structure. It reads: "Chimney Rock Dam." A small arrow points to the right.

What the sign doesn't tell you is how that cement slab ended up there.

Little Red Photography

When the Longmont Museum began its Dia de los Muertos celebration 18 years ago, the holiday was not well known -- at least not locally.

"That first year maybe 30 people came," said Ann Macca, the museum's curator of education.

Over the years, the event -- and the holiday -- has grown in popularity thanks, in part, to films like "Book of Life" and "Coco." Now the museum hosts one of the largest Day of the Dead events in the state with festivities occurring throughout the month of October leading up to the Nov. 1 and 2 holiday.