The sun beat down on Engi, making his already blistered skin even more pained. Days from the last refuge, he nevertheless pressed onward through the desert. The Rail here was something special, he was sure of it. Unlike the other Builder paths he'd mapped, this one went nowhere. Well, not exactly nowhere, he was sure, but whereas the others lead to obvious settlements and ancient cities, this spur went deep into the nothing.

Pausing in the shade of a narrow canyon, Engi slumped against the Rail to rest. There was a thunk and a clink as the canteen in his backpack was drawn to the magnetized steel. Prying it free, he uncapped the flask, the last of his sweetwater reserves. Feeling reckless, he took a big swig. Either he'd find something at the end of this spur, or he'd die alone. Commitment. The Rubicon had been crossed two days ago when he came onto the salt flats. Another day, or two at most, and he'd die of thirst. But it was four days back to the last stream he'd found. So forward it was.

He stood, and nimbly hopped onto the Rail, landing on a single, balanced foot in a way his simian ancestors would be proud of.

He'd heard the stories, of the ancient machines that would sail the Rails on invisible forces. Of course, he could do no such thing, but he still aped their image, sliding his forefoot along the metal, sweeping sand and dust off the narrow flat, while his back foot pushed him along. It was slow going, but he felt that in cleaning the Rail, he may be pleasing the Builders in some small way, and by this, that they might grant him favor in his journey.

Then he saw the first sign. It was carved into a cliff face, nearly twenty feet high.

It took a moment to understand, as it was a strange mix of pictograms and various languages, but he could just make out some basic understanding of it.

"This place is a message… and part of a system of messages… pay attention to it!"

Excited, Engi pressed on. There _was_ something here!

Another sign, this one in metal, like the Rail itself.

"Sending this message was important to us. We considered ourselves to be a powerful culture."

The Rail took a sharp bend at this point, parts of it nearly buried in a dune. Engi walked over the sand, finding the rail protruding on the far side. Too much to clean, so he moved on, hoping the Builders would understand.

"This place is not a place of honor… no highly esteemed deed is commemorated here… nothing valued is here."

Engi's heart rate doubled. Nothing of value doesn't get a sign saying nothing of value! Surely it was a test of the Builders. It must be something worth pursuing!

"What is here is dangerous and repulsive to us. This message is a warning about danger."

Now it gets interesting, Engi thought. But looking forward, he saw the Rail ended abruptly, at the foot of large cliff. Etched into the cliff, the signage continued.

"The danger is in a particular location… it increases toward a center… the center of danger is here… of a particular size and shape, and below us."

What danger? Engi wondered. Surely the Builders had many secrets, but the danger of their machines had died with them, centuries ago.

There was a cave, or maybe a tunnel. Engi left the Rail and approached, finding massive doors, sealed with more pictograms and bablespeak.

"The danger is still present, in your time, as it was in ours."

What is this place? Engi thought.

"The danger is to the body, and it can kill."

Or is it a bluff?

"The form of the danger is an emanation of energy."

But energy is power, Engi thought, and I want more of it. He pulled out his prybar and began to work at the doors as he read the rest.

"The danger is unleashed only if you substantially disturb this place physically. This place is best shunned and left uninhabited."

A bluff, he knew, for the Builders were jealous and wanted no one to take their power. He continued to pry, and eventually was rewarded with a hiss of pressurized-yet-stale air.

Coughing in the dust, he turned on his lamp and moved into the tunnel. Another sign greeted him.

"Welcome to Yucca Mountain."