What Causes Indentation On The Crown Of The Skull?

I have recently noticed an indentation on the crown of my skull. I've never noticed this before and it seems oddly "dented". I'm just curious what could cause this and if it is natural. I dont have any other symptoms such as headaches or blurred vision. I've read online about others with this condition and their test results didn't show anything. Therefore, I'm not sure I want to spend large sums of money for tests only to find the same results.