Jamieson, Fausset and Brown on Jeremiah 51:25

25. destroying mountain--called so, not from its position, for it lay low (Jr 51:13; Ge 11:2, 9), but from its eminence above other nations, many of which it had "destroyed"; also, because of its lofty palaces, towers, hanging gardens resting on arches, and walls, fifty royal cubits broad and two hundred high.

roll thee down from the rocks--that is, from thy rock-like fortifications and walls.

burnt mountain--(Re 8:8). A volcano, which, after having spent itself in pouring its "destroying" lava on all the country around, falls into the vacuum and becomes extinct, the surrounding "rocks" alone marking where the crater had been. Such was the appearance of Babylon after its destruction, and as the pumice stones of the volcano are left in their place, being unfit for building, so Babylon should never rise from its ruins.