The 'sea of glass' in front of God's throne (Revelation 4:6) is just decorative scenery

This one is thinner than most, so it's worth saying up front rather than pretending otherwise. Revelation 4:6 places "a sea of glass, like crystal" directly in front of God's throne, inside a vision John builds by blending Daniel 7, Ezekiel 1, and Isaiah 6 into one throne-room scene. In most casual readings this detail gets treated as set dressing: something John threw in because a throne room needs a floor.

One scholarly reading that does get raised (Bruce Malina's astral approach to Revelation) ties the sea of glass to the "firmament": the solid dome of sky the Old Testament pictures God's throne as resting above (Genesis 1:6; Job 37:18; Psalm 29:10). On that reading, God's throne sits above the vault of the sky, and the glassy sea is that vault seen from inside the throne room. It fits the wider pattern of the chapter, where thunder, lightning, and storm phenomena all point back to the Sinai theophany and a sovereign God ruling from above creation.

That reading, though, is explicitly flagged as a speculative, minority angle: one Heiser calls worth including but doesn't treat as settled. Nothing in Heiser's own material develops the sea of glass much further than that single line. So the honest verdict is that the popular claim ("it's just scenery") is probably wrong, since everything else in the vision is doing real symbolic work, but exactly what job the sea of glass is doing isn't something the sources spell out with confidence.