What does sacred space look like for the Church today?
The theology is pretty clear, but there’s different ways to apply it, and it makes a big difference which direction you go.
The theology is “Here we have no continuing city, but we seek the one to come.” The fire and storm that came on Sinai and that inaugurated the Temple sacrifices in Solomon’s day came on every head at Pentecost. From that day forward, sacred space isn’t a chunk of real estate in the same way that it used to be under the Old Covenant; the Spirit-indwelt believer is a portable mountain of God.
The commonest response to that reality is to ignore it, and just think of a church building as the “house of God” in the same way Solomon’s Temple was. Theologically, that’s a non-starter, but it’s very common.
The second most common application is iconoclastic: none of the buildings matter, it’s all just about the people now. This has curb appeal because it’s a very simple, straightforward application of the theology. Too simple, as it turns out. It misses two very important things.
First, in the immediate context of Hebrews, the same passage that says “we have no continuing city,” also says we need to do good and to share, “for with such sacrifices God is well pleased.” The book of Hebrews carefully develops a theology of new covenant priesthood in which Jesus replaces the old covenant priesthood with the far older priestly order of Melchizedek—and we come behind Him as our Forerunner. His sacrifice ends all sacrifice for sin, but there are still new covenant sacrifices, and we offer them as part of our priestly duty. He ministers, not in the earthly sanctuary, but in the heavenly sanctuary of which the earthly tabernacle was a copy. So there is such a thing as new covenant sacred space. It’s just in heaven.
But the iconoclasts are still wrong. Hebrews situates Jesus as our Forerunner and us as His younger siblings. Where He goes, we go. He goes behind the veil, into the heavenly sanctuary. We also offer sacrifices—the fruit of our lips, doing good, and sharing. When you’re a portable mountain of God and the Lord of Lords is your Forerunner, every beggar’s hand is an altar. The picture Hebrews paints is not that the sacred space is far away from us; we have been given the spiritual authority to call the sacred space down right here, right now, to offer our sacrifices in the presence of the Most High. That doesn’t mean there’s no sacred space on earth, that just means it moves: “here we have no continuing city.” We make the sacred space wherever and whenever we need to. Anywhere we offer our sacrifices, heaven meets us there.
Second, the iconoclastic move neglects the way God made us to be: humans exercise dominion over the earth. We build homes, shops, neighborhoods, cities—and that’s not some incidental factor or regrettable failing; it’s obedience to the first command God gave us (Gen. 1:28). We build things for purposes. A merchant has a store, a mechanic a shop, a chef a restaurant, an artist a studio, a teacher a classroom. From the Church’s earliest days, we gathered in multi-purpose spaces: principally homes, but also Solomon’s Porch, the School of Tyrannus, like that. It wasn’t until a few centuries in that we purpose-built spaces for the church to gather – not surprising, considering our quasi-legal status prior to Constantine.
Making a building for the purpose of gathering is the most natural thing in the world; it’s what we do for any other purpose. But constructing the building for that purpose does not make it sacred space. Sacred space is made when we, as new covenant priests, minister in the heavenly sanctuary. We do that all over town. And we can, and should, do it in the church buildings, too.
Full Contact Christianity 
Oh yeah. And that mountain? After the failure at Sinai where the Israelites were called to meet God “up there on top,” it reverted to its old name “Horeb,” and the focus shifted to Zion, the space “up there” where God reigns, to the gathering of the firstborn, of the spirits of righteous people made perfect.
Yes! And let me fill in the gaps with a little more resolution there. Where does God take for His dwelling place?
God meets them on Sinai. They beg off and send Moses as a mediator.
God has them make the Tabernacle as a portable mountain of God, and He dwells on the Mercy Seat, the lid of the Ark. He ultimately brings that to rest at Shiloh.
In response to Israel’s sin, God sacks Shiloh by means of the Philistines, and invades Philistia all by Himself, leaving Israel out of it. There, he makes conquest of their people and their god before returning with the spoils of victory to Beth Shemesh.
In response to the disrespect shown by Beth Shemesh, He conquers them too, and makes His home once again with Gentiles, in the Gibeonite city Kirjath Jearim (cf. Josh. 9:17).
There He remains until David attempts to bring the Ark to Jerusalem. Uzzah dies, and God makes His abode in the home of Obed-edom the Gittite (another Gentile–and from Goliath’s hometown, yet!). David finally brings the Ark up to Jerusalem, places it on Mt. Zion in the Tabernacle of David, and that remains God’s dwelling until Solomon’s Temple is completed and consecrated, and He moves into the Temple.
That temple remains God’s dwelling until He sacks Jerusalem by means of the Babylonians. There’s no temple for a time.
The temple is rebuilt on return from exile, and Zion is again the dwelling place of God, honored by God’s people, and in His turn by Jesus Himself. But the Temple rejects its role (“a house of prayer for all nations”) and its Messiah, and He’s slain outside the camp. He completes His superior priestly ministry in heavenly Tabernacle, the Zion above, and sends the Spirit, the very presence of God, at Pentecost on every head.
Per Hebrews, those on whom the Spirit came have no fixed abode on earth, but follow Christ in administering a superior priesthood in the heavenly Tabernacle, wherever on the globe they happen to be.
If 2 Chr 3:1 is accurate, Zion on earth started out as Moriah, and Abraham is thereby enshrined forever as our prototype of faith that “meets God on the mountain.”
Oooh. Good point!