Remember when we were kids we were told that if we dug a hole deep enough we would end up in China? Well, we found that hole and it does go to China.
Long story short: We rode our bikes to a small ethnic village where we were immediately harassed by dozens of women to buy hand-made souvenirs. After buying a few things Huyen told us that there was a cave at the end of the town. We jumped back on our motorbikes and drove to the cave.
When we arrived outside the cave we were immediately harassed by dozens of little kids, who I could only assume were the children of the women who had just harassed us. Like mother like son. The kids were all peddling flashlights to rent for the cave. After some tough negotiations we each got our own flashlight AND a kid to be our tour guide. I had assumed the cave was just a few feet deep but before we knew it we were climbing up walls and following a tiny underground stream. After going for about fifteen minutes Huyen told us that our guide wanted to know how much father we wanted to go. We naturally asked how much farther we could go. That's when we found out this ridiculous fact -- THE CAVE GOES TO CHINA.
Rather than risk being turned around at the other end for not having our passports, we decided to go back. But come on, are you serious! We found a tunnel to China!