As Jesus walks out of the place of worship, the temple, the comment is made that the building look great. Then Jesus, even though He actually agrees that the buildings are great, points out that they're just buildings and are going to be torn down (which they were when Jerusalem was destroyed in 70AD). But the church isn't a building - it's the people who are part of kingdom that the gates of Hell won't overcome. There's nothing wrong with a church building but having one or not doesn't make a church - having a group of people who are followers of Jesus is what makes a church.

Mark 13:1-2