There are 32 Secret Areas in Saints Row 2. Upon reaching each location for the first time, a "(location name) found" message is displayed on-screen, but they are not indicated on the Map, and there are no visual indicators apart from the initial on-screen message.
They are counted in both the Diversions menu, and the Statistics Menu, but there is no reward for finding them all.
Some of the locations are encountered during the main storyline, but many are unlikely to be visited without deliberate exploration.
The game data files refer to the Secret Areas Diversion as Exploration, and is part of the same diversion as exploring neighborhoods. The on-screen message is in the same style as neighborhood notification messages.
Unlike other Collection Diversions, Secret Areas are not numbered.
At the Nuke Launch Room, there is a .44 Shepherd model sitting on the table, surrounded by blow-up dolls.
The game data files mention a 33rd location named "Old Bar", but does not define the coordinates. This may refer to Sea Roses, an empty bar in Sunnyvale Gardens.
The capitalisation style of each location varies, with some using title case, and others using sentence case.