this place is best shunned and left uninhabited  

mammoth has an interesting post on ways of making nuclear waste sites recognisably dangerous over long periods of time - this place is best shunned and left uninhabited.

Triggered by the recent revelation that tests at the Pacific Northwest National Laboratory reveal that a seemingly innocuous white substance filling a glass bottle dug up in 2004 is actually “the oldest existing sample of bomb-grade plutonium from a nuclear reactor, with a half-life of 24,110 years,” Juliet Lapidos reviews the Department of Energy’s 1993 recommendations for the construction of a massive nuclear-waste disposal warning landscape. The trouble, of course, is that anything one does to communicate danger is likely to also communicate mystery and excitement to future treasure-hunters or archaeologists:

The report’s proposed solution is a layered message—one that conveys not only that the site is dangerous but that there’s a legitimate (nonsuperstitious) reason to think so. It should also emphasize that there’s no buried treasure, just toxic trash. Here’s how the authors phrase the essential talking points: “[T]his place is not a place of honor … no highly esteemed deed is commemorated here.” Finally, the marker system should communicate that the danger—an emanation of energy—is unleashed only if you disturb the place physically, so it’s best left uninhabited.

As for the problem of actually getting these essentials across, the report proposes a system of redundancy—a fancy way of saying throw everything at the wall and hope that something sticks. Giant, jagged earthwork berms should surround the area. Dozens of granite message walls or kiosks, each 25 feet high, might present graphic images of human faces contorted with horror, terror, or pain (the inspiration here is Edvard Munch’s Scream) as well as text in English, Spanish, Russian, French, Chinese, Arabic, and Navajo explaining what’s buried. This variety of languages, as Charles Piller remarked in a 2006 Los Angeles Times story, turns the monoliths into quasi-Rosetta stones. Three rooms—one off-site but nearby, one centrally located, and one underground—would serve as information centers with more detailed explanations of nuclear waste and its hazards, maps showing the location of similar sites around the world, and star charts to help intruders calculate the year the site was sealed…

Proposals for the “earthworks” component demonstrate that the whole project of communicating with the future is really a creative assignment, more dependent on the imagination than on expertise… The report proposes a “Landscape of Thorns” with giant obelisklike stones sticking out of the earth at odd angles. “Menacing Earthworks” has lightning-shaped mounds radiating out of a square. In “Forbidding Blocks,” a Lego city gone terribly wrong, black, irregular stones “are set in a grid, defining a square, with 5-foot wide ’streets’ running both ways. You can even get ‘in’ it, but the streets lead nowhere, and they are too narrow to live in, farm in, or even meet in.”