Come see the castles at the Emporium. There is the Ceridwen Castle, with ethereal hues and hidden rooms; there is the Caerwyn Fortress - a half sim complex based on the 13th century Harlech castle in Wales, with lots of hidden doors and spaces and a large interior courtyard; and there's the Caerwyn Keep, which is the castle portion of the larger fortress.

You can see them all by clicking on the Castles sign under Viewing Platforms. See if you can find all the hidden passages.