Answer:
Halo of water, tongue of wood. Skin of stone, long I've stood. My fingers short reach to the sky. Inside my heart men live and die.
Twigs and spheres and poles and plates. Join and bind to reason make.
What word starts with 'E', ends with 'E', but only has one letter? It is not the letter 'E'.
A certain wizard resided in a city made from this gemstone.
I hide but my head is outside.
Both old people and owls are said to be possessing this trait