You made me see if anyone is remaking it-
was not disappointed, I found something in pretty early stages. https://bitbucket.org/dalerank/caesaria/wiki/Home
Now I just wish someone would remake them all with a single engine re-do, (Pharaoh, Zeus, Ceaser 3, Emperor) and allow for infinite mining/trading (for pyramid building), larger maps, and having an engine people could build additional city building shit for.
There is an open source version of Caesar III, but I just spotted a problem for you.
They used to include all the original graphics there, but I just found out they now require the original game for the graphics and sounds.
I'm still going to leave this comment because someone else might find it useful. Sorry about this, I thought you could have at least played the open source version. :(