ATLAS-I is world's largest wooden structure, but what it was used for is even more impressive.
Built between 1972 and 1980 on Kirtland Air Force Base in Albuquerque, New Mexico, the ATLAS-I facility was intended to test the electromagnetic pulse (EMP) resistance of flying aircraft. It did this by producing an actual EMP without the help of a nuclear weapon - which was formerly a requirement for EMPs.
The massive structure consists of a 180 meter-high platform, which was constructed with wood in order to avoid interfering with the EMP waves it generated. The largest piece of the structure is the support platform, on which aircraft could be parked for EMP tests when the facility was still in operation.
The EMP was generated by a 200 GW pulsed Marx Generator with a voltage of 10 MV.
The facility stopped operation in 1991, when the much safer and cheaper option of computer simulations where developed, but still it sits, abandoned. Now considered a major fire hazard, efforts are being made to give it national landmark status for preservation, despite the complication of it being located on a military base with top secret status.