Oldest Corner Stone in Prague

This is probably the oldest corner stone in Prague. As you see it's not very attractive, but still tourists are coming to see it - at least 6 people came to see it while I was there(15mins). If somebody is wondering what corner stone is for, here is short explanation: Corner stones served as protection of corners in 19. century when horses with heavy carriages used to damage them as riding around. Of course, a cache can be found nearby: GC14FDZ.