In 1993, Sandia National Labs published a document that contained the following words:
The danger is still present, in your time, as it was in ours. The danger is to the body, and it can kill. The form of the danger is an emanation of energy.
Sandia National Labs had undertaken the task of designing a radioactive waste facility in New Mexico meant to last 10,000 years — the US Department of Energy's Waste Isolation Plant (WIPP). The contents of this facility is toxic and harmful to humans. They needed to find a way to keep people out.
They setup expert panels to help design sugh a facility. In 1993, they published their findings
First they importantly recognized that, past 100 years, there is no guarantee that there will be organized oversite of such a facility:
Active institutional controls are considered effective for no more than 100 years. (F-19)
In other words, they recognized that, past 100 years or so, Sandia National Labs may not exist. For that matter, the United States of America may not even be functioning. They therefore recognized not only a need to make the facility structurally last, but also a way to communicate to future civilizations about the dangers contained within the facility. They wanted to prevent intrusions by future treasure seekers:
Certain time periods after the end of the expected 100 years of active institutional control after closure (100-300 years, 300-3,000 years, or 3,000-10,000 years after closure) [...] were considered [...] (1-9)
Physically keeping people out for 10,000 years was considered impractical, so the teams set out instead to deter would be intruders. Some intruders, it is presumed, may inadvertently discover the site while others may intentionally excavate it. They complete there survey by assuming three different levels of technology: High (beyond 1990's), Medium (on par with the 20th century) and Low (the intruders may have regressed into a more primitive technological state). Everything from future archeaeological investigation to simple drilling for water was considered.
The teams got a little carried away, it seems. When describing how the site should be marked, one team stated:
The method of site-marking must be very powerful to distinguish this place from all other types of places, so that the future must pay attention to this site. The place’s physical structure should strongly suggest enhanced attention to itself and to its subelements. To achieve this, the volume of human effort used to make and mark this place must be understood as massive, emphasizing its importance to us. The site’s constructions must be seen as an effort at the scale of a grand and committed culture, far beyond what a group or sect or organization could do. (F-50)
It's not entirely clear what that team expects Sandia or the US DoE to be able to accomplish. The real fun comes right before that, however. When describing what the architecture of such a site should convey, they came up with this bit of prose:
This place is a message... and part of a system of messages... pay attention to it! Sending this message was important to us. We considered ourselves to be powerful culture. This place is not a place of honor... no highly esteemed deed is commemorated here ...nothing valued is here. What is here was dangerous and repulsive to us. This message is a warning about danger. The danger is in a particular location... it increases towards a center... the center of danger is here... of a particular size and shape, and below us. The danger is still present, in your time, as it was in ours. The danger is to the body, and it can kill. The form of the danger is an emanation of energy. The danger is unleashed only if you substantially disturb this place physically. This place is best shunned and left uninhabited. (F-49)
Oddly enough, I disagree with the framework of their assessment. They try to call attention to the site by waving a big danger flag over it. Yet, no structure is going to last 10,000 years; it will either end up toppled over or buried. If it does somehow last, it will surely be forgotten about in the middle of the desert. And if it's not forgotten about — if responsible entities keep watch over the site — then the exercise will have been for nought anyways.
A better idea, it seems to me, is to hide it for as long as possible. Make it inconspicuous. Bury the material deep and make the entrance inconspicuous; perhaps bury that even.
However, also build a large wide antechamber over the site. Ensure that anyone inadvertently digging or drilling in the area first enters the antechamber. Put all your big scary warnings in there. I agree with some of their specifics — ensure that your warnings are foreboding but cheaply constructed.
In the end, the site was built in 1999 and is rather dull looking. You can see a few images on their website. It seems to me that they have in fact completely failed at their initial goes. Were the building abandoned today in its current state, it would be highly intriguing to future civilizations, having nothing foreboding or alarming about its structure. It's clearly of value to those who built it. Why not have a look?