At this spa, I was able to bathe in volcanic sand — a treatment that the spa said quells muscle soreness and detoxifies skin (via sweating). During this treatment, I was buried under heated sand, which caused me to sweat so much, the clothes I'd borrowed were completely drenched. The timer was set to 15 minutes, but I only lasted 10 — and I chugged water. I was so thirsty and exhausted after the treatment (like I'd gone for a long run), but my skin felt incredible.
It's important to note that during this treatment, I was careful to listen to my body and hop out once I felt like I might have been overheating.