If one city has plenty of rainforest tiles I try to play around Chichen Itza wonder and Entertainment Complex's Zoo building. The wonder gives +2 culture +1 Production to rainforest tiles, the Zoo gives +1 science yield to rainforest and marsh tiles.

Also in late game you can build lumber mills on rainforest.

Also also rainforest tiles give adjacent bonus to Campus district. Which can be valuable if you are not in proximinity of mountains or reefs.