When Jesus told Peter upon this rock I will build my church, Jesus is the rock, the foundation upon which to build.  Jesus was not saying upon this rock I will build a 5,000 sq. ft. building with glass stained windows.  Jesus said the gates of hell shall not prevail against the church (body of believers). For instance, the early church was under intense opposition, persecution and attacks from the gates of hell, but Jesus conquered the grave so that the gates of hell (power of death) will not prevail or defeat those who are in Christ.