A couple exceptions do in fact exist where the site is relatively flat and the theatre is not built into the slope of a hill or ravine but entirely built up from level ground. One such exception is Metapontum in Basilicata.
Cross? What cross? Was there really a noteworthy one? That seems quite doubtful.
More detailed answer:
A first thought is of course that the depictions shown so far are not entirely realistic. Icons have a halo, real people do not. Churches are marked in pictures with a cross, they do seldom have one in reality, very seldom if it should be ...