Over the past 30 years, physicists have failed in their attempts to uncover the secrets of dark matter.
Now, by building an unparalleled state-of-the-art detector in Sanford, South Dakota, researchers are closing in on the answer to one of the most persistent problems in science. If they fail, it may leave more questions than answers.
Mega Builds is a video series from BBC Future looking at giants of engineering from around the globe.
Video script: Henry Roberts