'Sea of Glass' in the Bible

And before the throne there was a sea of glass, like crystal. And in the middle of the throne, in the circle about the throne, there were four living creatures, full of eyes, before and behind.

And I saw, as it were, a sea of glass mingled with fire; and those who overcame the beast, and its image, and its mark, and the number of its name; standing by the sea of glass, having the harps of God.