I have a square base and rise to a single point, but I'm not a party hat. I was built by ancient hands, but I'm not a ruin in the traditional sense. I hold secrets within, but I'm not a diary. What am I?

In the green garment of the earth, I rise with a gentle grace, a natural knoll nudging the sky, where wanderers rest and winds whisper tales.

The waves of land are what I be, A smaller mountain, as you can see. I might have been in your childhood, Where you might have rolled down me, like wood.

A surface of glistening waves is what I'm made of, sometimes to large to see the far end. Yet an ocean or sea I am not. Naturally I am filled, tho all round the year humans find a way to have fun with me.

I have no voice, yet I’m full of names. I never move, yet traffic flows on me. I can be long or short, rich or poor, Homes face me, footsteps mark me, and cities are built upon me. What am I?