Downloading Hidden Expedition: Smithsonian Castle 2.0 for Mac from the developer's website was possible when we last checked. We cannot confirm if there is a free download of this app available.
Some of the application aliases include "Hidden Expedition SmithsonianCastle SE", "Hidden Expedition Smithsonian Castle". This program was developed to work on Mac OS X 10.4 or later. This software for Mac OS X was originally created by Eipix Entertainment. We recommend checking the downloaded files with any free antivirus. The program lies within Games, more precisely Puzzle. The most popular version of Hidden Expedition: Smithsonian Castle for Mac is 2.0.
From the developer:
Hidden Expedition: Smithsonian Castle is an adventure hidden object game for Mac. Your old buddy and H.E.L.P. operative Sam calls you in to investigate a strange anomaly at the Smithsonian Castle. You soon learn there's more to this anomaly than meets the eye, and H.E.L.P's reach stretches back to the Smithsonian's historic founding.
You may want to check out more software for Mac, such as Hidden Expedition: Smithsonian Castle Collector's Edition, Hidden Expedition - Devil's Triangle or Hidden Expedition Uncharted Islands, which might be similar to Hidden Expedition: Smithsonian Castle.