It was released on Jan 19, 2011 as part of the Valentine's Day Event (2011). Like the Haunted House and the Winter Workshop, you can harvest the castle for Valentine's Gifts (2011) to use in the Valentine's Box (2011). You can also harvest your neighbors' Cupid's Castle.
Cupid's Castle is also used in the Valentine's Day Quest.
Building Stages Edit
A glitch in the system meant that sometimes a completed castle would 'grow' 2 or 3 times as big. This can be resolved by simply reloading your farm or refreshing the page. Also, when you visit your farm on the iPhone, even though you have completed the castle, it will show it is not completed.