Legia by Edgar Allen Poe

The room lay in a high turret of the castellated abbey, was pentagonal
in shape, and of capacious size. Occupying the whole southern face
of the pentagon was the sole window --an immense sheet of unbroken
glass from Venice --a single pane, and tinted of a leaden hue, so that
the rays of either the sun or moon, passing through it, fell with a
ghastly lustre on the objects within.