There's really nothing special about that building...

Code:
building amphitheatres
{
    levels game_field stone_amphitheatre zurkhaneh small_gymnasium urban_amphitheatre gymnasium great_amphitheatre palaistra gymnasiumacademic
    {
        game_field requires factions { all, }
        {
            capability
            {
            happiness_bonus bonus 1
            recruits_exp_bonus bonus 1 requires factions { barbarian, armenia, scythia, pontus, }
            }
            construction 4
            cost 1600
            settlement_min town
            upgrades
            {
            	stone_amphitheatre
            	zurkhaneh
		small_gymnasium
            }
        }
Possibly the bolded line carries a risk with it in rebellions? I'll try removing this line in this savegame when I get home on Monday, if noone has tested it before then.