When the beautiful, impregnable castle ceases its defensive function and turns into an invitation, watch what happens. Here come the tourists and sightseers, finally breaching those stalwart and famous walls!
That the castle was so stalwart is what allowed it to survive to its present renown and be categorized as historic! The protection it provided is what has drawn the horde of tourists, their excessive presence now making a mockery of its former purpose! And despite the short-term economic benefit to any region that harbors such landmarks, these tourists, made so by their disposable income and clearly even more disposable time, in the end, accomplish what the fiercest warriors of yesterday, the most feared enemies of the defenders of the great castle (and so, through contact, granted a share of greatness themselves) were never able to do: they have breached the walls!
Oh, the gates open and in flood the Americans, letting in the fabricated world they’ve created. (America, of course, did not create tourism and travel, but it mass-produced it, I would argue.) And even this might not be so bad if it weren’t for the fact that it never ends with a crowd of sightseers.
No, they are merely the sign that a society’s defenses have become decorative, their cameras illuminating a weakened target. The sightseers ultimately leave a legacy of sight-taking. See the historical city as it takes its last organic breaths, gorging unconcerned on a fool's gold economic windfall, enticing the next generation of invaders and raiders!
Tourists break the best defenses and, given enough time, reveal why they were needed to begin with.