The Spanish EQ that recently was giving +5 stability cannot be built in cities that are mutinous or worse despite providing much needed stability. The Roman Triumphal Arch likewise so, unable to be built in mutinous cities, as much as it's possibly stability gain is needed.

Seconded.  I found this while playing last night; as the Romans, I conquered Athens, and those mutinous Greeks let me wait far too long before I could build a triumphal arch to commemorate my victory over them. :P