John Calvin on Rome:

For both the writings of holy fathers, the acts of councils, and all history, make it plain that this height of power, which the Roman pontiff has now possessed for about four hundred years, was attained gradually, or rather was either craftily crept into, or violently seized. But let us forgive them this, and let them take for granted that primacy was divinely bestowed on the Romish see, and has been sanctioned by the uniform consent of the ancient church; still there is room for this primacy only on the supposition that Rome has both a true church and a true bishop. For the honor of the seat cannot remain after the seat itself has ceased to exist. John Calvin, The Necessity of Reforming the Church (Dallas: Protestant Heritage Press, 1995), pp. 133-134.

Can she be the mother of all churches, who not only does not retain, I do not say the face, but even a single lineament, of the true church, and has snapped asunder all those bonds of holy communion by which believers should be linked together? John Calvin, The Necessity of Reforming the Church (Dallas: Protestant Heritage Press, 1995), p. 135.

The Roman pontiff is now opposing himself to the reviving doctrines of the gospel, just as if his head were at stake. Does he not, by this very fact, demonstrate that there will be no safety for his see unless he can put to flight the kingdom of Christ? Your imperial majesty is aware how wide a field of discussion here opens upon me. But to conclude this point in a few words: I deny that see to be apostolical, wherein nought is seen but a shocking apostasy; I deny him to be the vicar of Christ, who, in furiously persecuting the gospel, demonstrates by his conduct that he is Antichrist; I deny him to be a successor of Peter, who is doing his utmost to demolish every edifice that Peter built; and I deny him to be the head of the church, who by his tyranny lacerates and dismembers the church, after dissevering her from Christ, her true and only Head. John Calvin, The Necessity of Reforming the Church (Dallas: Protestant Heritage Press, 1995), p. 135.