As someone who's worked on laboratory ultra-high vacuum systems the ~2m diameter by 4km long arms that are vacuum chambers are quite impressive.
A "fun fact" from the tour was that they had a road grading company construct the underlayer for the support of the arms. They asked the company to set the angle of the grading to equal the negative curvature of the earth as the arms have to be straight in space while a surface that's graded "flat" would end up following the curvature of the earth.
https://goo.gl/maps/9fLFCVqjumx1LSkXA
As someone who's worked on laboratory ultra-high vacuum systems the ~2m diameter by 4km long arms that are vacuum chambers are quite impressive.
A "fun fact" from the tour was that they had a road grading company construct the underlayer for the support of the arms. They asked the company to set the angle of the grading to equal the negative curvature of the earth as the arms have to be straight in space while a surface that's graded "flat" would end up following the curvature of the earth.