Deep under the craggy volcanic landscape, ice takes on weird and wonderful forms: spiky sheets of icicles, miniature frozen spires, glazed rock faces, and a hoarfrost-sprinkled ceiling that sparkles like the night sky. Every Saturday from January to March, six lucky visitors can see it firsthand on a three-hour guided tour of Crystal Ice Cave, where they’ll scoot down a frozen slide, wiggle through tight passages, and squeeze behind an ice waterfall. For your best shot at a spot, call right at 8:30 a.m. three weeks before your desired date. And don’t delay—climate change is melting surface ice, which seeps into lower caverns and refreezes, sealing off more and more of the cave every year. Season January to March Permit Free; reservations required. Call (530) 667-8113.