If you can get the goods, e.g. through your guild, Himeji Castle is superb. I have an IA city on beta and replaced a load of productions with HC. It took up less space in total, and gives many times the number of supplies even on a very low level. If events call for it, I put down some blacksmiths, which still take up less space and pull them up when event ends to put down the event building in the space.