The Allen and Greenough is still under construction;
so some links may not work quite the way you would expect.
THE ABLATIVE AS LOCATIVE.
Ablative of Place.
421. The Locative Case was originally used
(literally) to denote the place where and (figuratively) to denote the
time when (a development from the idea of place). But this case was
preserved only in names of towns and a few other words, and the place
where is usually denoted by the Ablative. In this construction the
Ablative was, no doubt, used at first without a preposition, but
afterwards it became associated in most instances with the preposition in.