Where does God live?
The tongue-in-cheek answer is, "Anywhere He wants." He is, after all, God, and He is transcendent, and He is everywhere and anywhere and nowhere all at once.
The "church" answer is, "In my heart." This is what we teach our children and, in some cases, our seekers - that Jesus makes His home in our hearts and dwells within us in our inmost places. That we are the house of God in our own flesh.
But the question is more complicated than either of those answers portrays, and it deserves a lot more conversation than we tend to give it.
From relatively early on in the story of God, His people have consistently been concerned with where God is going to live. Moses built a tabernacle in the wilderness to make sure that God had a dwelling place among them, which served a few purposes - it gave God a place to dwell, protected the Israelites from seeing Him face-to-face in the smoke and the fire, and provided a place for the people to come together to worship. Even after Israel settled in the Promised Land, they continued tabernacle worship for many generations.
There were altars built throughout the land, and for awhile, the people went to these altars to find God. They were usually just piles of uncut stones, but they were the places where Israel knew they would find God.
When David is working on building his palace, he can't shake the realization that he's going to have a place to live, but God is not. So he starts developing in his heart the plans to build a temple for the Lord, although the Lord stops him from actually following through with it. Instead, David made the plans and began gathering the materials, but it was his son, Solomon, who actually built the Temple.
From then on out, we had a Temple people - and the dwelling place of God was central to their lives. They didn't consider themselves defeated until their Temple was destroyed, and when the exiles came back, it was the Temple that they were interested in rebuilding. It was important to God's returning people that God have a place to dwell among them first.
We get to Haggai, and this is a prophecy at the time of Israel's return from Persia, and God is basically chastising His people for worrying more about their own houses than His, for rebuilding their own homes before they rebuilt His.
Even in the New Testament, we see this: at the Transfiguration, Peter chimes in and says what a great thing it would be for them to build three tents, so that God has a place to dwell there among them on the mountain.
Throughout time, then, it has always been important to God's people where God dwells. And if that's true (and, as we've said, it is), then it's still an important conversation for us to be having today.
So let's have it.