Upgrades - Special
These upgrades don't really fit in with the common notion of upgrades but they do enhance the way your City earns.
These special buildings come in the form of rare buildings that can be unlocked by spending bux.
Their cost range from a relatively cheap to really expensive. Also, you cannot have more than one in your City.
These buildings are automatically marked as Historical if they are built by the random lot upgrades when a build is triggered. They earn a percentage more than regular buildings.