This is a fragment of marble from the seating section of the Collosseo - you can't really see well but carved into the rock are some gladiator figures with their names - apparently some fans really liked a couple of them.  Engraved in the piece next to it is the exhortation - "Cheer!".  There are several other fragments where families have carved their names in order to stake claims to'their' seats - apparently they were having problems with low class bounders horning in on the good seats...