BLUE MOUNDS, WI (AP) -

The Cave of the Mounds in Dane County is offering a unique Christmas experience.

It is featuring holiday carolers singing in the caves. Organizers say the voices and music in the natural caverns produce unique sounds.

There are four concerts in December, a walking tour and sing-alongs every Sunday in December.

A portion of the proceeds are donated to a charity chosen by the performing group. Tickets are available online or at the door. Space is limited.