The Emperor's Entrance comes with the special set bonus. When it is adjacent to other buildings belonging to the Cherry Garden Set the properties of the building are improved.
The Emperor's Entrance can be upgraded by Emperor's Entrance Upgrade Kit item. To upgrade the Emperor's Entrance, use the Emperor's Entrance Upgrade item on the Emperor's Entrance that is already situated in your city. Its upgraded version will then be placed directly on the same spot in your city and the production timer will not be reset. Note that the upgraded building will be from your current era, even if the old one was from one of the earlier ages.
Every 24 hours the Emperor's Entrance will produce the following resources. Base resources will always be produced. Bonus resources are determined by how many other unique Cherry Garden Set buildings it is connected to.