mythologyandhistory, 
Did you know that #Roman road design included #safety features?
In the ruins of #Pompeii, you'll notice small white stones interspersed with the large paving ones along the extensive roads.
Those white #stones are 'cats eyes', i.e. gems that have a single line of inclusion of crystals of another mineral inside.
Upon light reflective on them (from the #moon), they enable the walker to see that they are still on the right path!
