[lgleason]

I recently left a project that demonstrated most of these traits. Usually these things are the top of the ice-burg.

[teddyh]

Know your burgs and bergs. A “burg” (or burgh) is a fortification, or more usually refers to a city built around (or inside) that fortification. A “berg” is a mountain, or a large hill. Therefore, an iceberg is an “ice mountain”, and a “burgermeister” is a “city master”; i.e. a mayor.

[de_watcher]

You forgot to mention that you should use "tip" instead of "top" in this idiom.

Here is a video with more detail: https://www.youtube.com/watch?v=dQw4w9WgXcQ