Ascensions to heaven and descents from it, "translations," "assumptions," "annunciations," mortals "caught up" into it and returning, angels flying between it and the earth, thunderbolts hurled down from it, mighty winds issuing from its corners, voices speaking from the upper floor to men on the lower, temporary openings of the floor of heaven to reveal the blessedness of the good, "signs and wonders" hung out from it to warn the wicked, interventions of every kind--from the heathen gods coming down on every sort of errand, and Jehovah coming down to walk in Eden in the cool of the day, to St.Mark swooping down into the market-place of Venice to break the shackles of a slave--all these are but features in a vast evolution of myths arising largely from this geographical germ.
Nor did this evolution end here.

Naturally, in this view of things, if heaven was a loft, hell was a cellar; and if there were ascensions into one, there were descents into the other.

Hell being so near, interferences by its occupants with the dwellers of the earth just above were constant, and form a vast chapter in medieval literature.

Dante made this conception of the location of hell still more vivid, and we find some forms of it serious barriers to geographical investigation.
Many a bold navigator, who was quite ready to brave pirates and tempests, trembled at the thought of tumbling with his ship into one of the openings into hell which a widespread belief placed in the Atlantic at some unknown distance from Europe.

This terror among sailors was one of the main obstacles in the great voyage of Columbus.