Ezekiel 41:16

¹⁶ The thresholds, and the oblique windows, and the galleries round about on three sides, over against the threshold of every one, and floored with wood all round about: and the ground was up to the windows, and the windows were shut over the doors.

Holy Jerusalem

In Revelation 21:2, this signifies the Lord's kingdom in heaven and on earth -- the foundations of which are holy truths. (Arcana Coelestia 1298)