A replica of Ashokan Rock Edict (National Museum, New Delhi). I think to use naturally occuring rock structures in villages, cities, for communicating with people was a very economically smart idea of Ashoka. And aesthetically (and artistically) pleasing as well. Plus, rocks are one of the most durable writing media (the writings survived all weather conditions for 2500 years and still going strong!). Attached is a photo of rock edict (replica) for your visual pleasure