The Courthouse is replaced by the following unique buildings:
Courthouses reduce your expenses and grant you Espionage points. Each Courthouse halves maintenance for its home city. Maintenance increases with each further city you found, so building Courthouses helps to offset the spiralling costs. Once you have built enough Courthouses, you can build the Forbidden Palace, which further reduces maintenance. Courthouses also give a bonus to espionage and enables you to have one Spy specialist, which produces more espionage.
As kingdoms and empires expanded, it became increasingly difficult for the rulers to maintain control over the more distant regions of their realm. To ensure that the far-flung cities of the empire contributed their expected share of duties and taxes to the government, rulers constructed courthouses to help unify their domains. These local centers of government meted out justice and helped preserve order in the midst of the furthest wilderness.