This was my first time to explore the old town part of San Juan and I wasn't disappointed. I also learned a thing or two! When the Spanish came over to start hauling gold away in their ships, then brought these blue cobblestones from Spain as ballast. So, upon arriving at the port of San Juan, they would dump all the blue cobblestone before filling up with gold. The locals would use all the pretty blue stone to pave the streets. Pretty nifty eh?