CSA0622: [S] Cottagesnagged
Far off at the unfashionable end of a Japanese mountain range lies the old, decrepit Hakurei Shrine. Given the general state of disrepair, the effects of weather and so on, the evidence suggests that it has been abandoned for a couple of decades, give or take.
Which is a bit odd, because it was actually abandoned about a hundred and fifty years ago.
In truth, the Shrine is a gateway to Gensokyo, the Land of Illusion. The premise is simple: if there is sufficient active disbelief in any phenomenon in the Outside World, or at least if it passes into legend, it is possible for it to appear in Gensokyo, perhaps spontaneously. And so it is filled with magic and monsters and youkai of all descriptions, as well as a few species of mundane flora and fauna which are extinct in the Outside World. Books related to the moon landings and such things, too, if enough people start believing it was faked.
It was easily-accessible until Yukari Yakumo, the Mistress of Boundaries and Sage of Youkai, realized that as far as magic was concerned, Earth was going to hell in a handbasket. If nobody did anything, magic might completely die out. Thus, 174 years ago, in 1884 by the Outside World's calendar — and so, the year is now 174 by Gensokyo's calendar — she and the miko of the Hakurei Shrine erected the great Hakurei Barrier around Gensokyo, sealing it away from the increasingly-scientific Outside World. Magic is now preserved, protected, and hidden.
The Hakurei Shrine is inside Gensokyo too, of course. This version merely looks like upkeep has been a bit perfunctory lately.