"Now it came to pass, afterward, that [Jesus] went through every city and village, preaching and bringing the glad tidings of the kingdom of God. . . . And [the formerly demon-possessed man] went his way and proclaimed throughout the whole city what great things Jesus had done for him."
Here is a great pattern of how true Christianity works. Jesus' gospel is proclaimed from the church's pulpits, the cities of the world are filled with Christ's doctrine (cf. Acts 5:28b), and the individually-redeemed saints bring this good news to everyone they can.
Today, just like then, what Christ preaches through His clergy, the parishioners proclaim in their worlds and spheres of influence. In this way "every city" and "whole cit[ies]" are reached with the gospel of grace.
[Puritan quote of the day: "What would become of us if there were not grace above sin, and mercy above misery, and power in Christ Jesus above all the power in Satan and death?" --Richard Sibbes, in "Glorious Freedom"]
