Grimrock

Hi guys

I have an iron key from the crystal mines but I can't find a place anywhere to use it I've been wondering around for hours now!

Also I notice in the puzzle room called only the fearless may pass there at the end of the corridor there appears to be two different areas under the bridges does anyone know how to get to these areas at all?

A thousand thank you's to anyone who can help

There is a hidden button at the entrance to the mine. About the key.... sorry i dont remember where to use it but it must be around.

Any help is appreciated thank you!

The iron key is probably from the pit-puzzle outside and it's used in the sewers area.