Are there any hidden places on club penguin?

Some "secret" places on Club Penguin are: The Underground Pool (go to Plaza and waddle to the manhole. The Iceberg. Look to the top right of the map and you will see a little Iceberg. Click it. Here, you can also play "Aqua Grabber".
These days there are hardly any places that are really "secret", but I'll list a few.

• The iceberg! It's the white iceberg thing at the top right corner in the map.
• The mine.
• The Dojo (well, it used to be secret, although now it has an icon all to itself).