Available in MAKE: Volume 52, their writer Scott Dalton had the opportunity of a lifetime – he was allowed access to VALVE’s secret hardware prototyping laboratories, to take a look at how they built the HTC vive. Yup, that’s VALVE’s handywork.
What he found, can only be described as awesome. From things like this:

The Susan – One of VALVE’s first VR prototypes. Photo by Make: Magazine.
All the way to things like this:

Early prototype of lighthouse – VALVE’s tracking system for the VIVE. Photo by Make: Magazine
The full article that contains several galleries of photos and a video interview with Alan Yates and Monty Goodson – the folks behind this, can be found on Make: Magazine