This brings back memories! I worked at NASA Ames about 10 years ago, and even at that time most of the wind tunnels had been decomissioned with the exception of the 80x120 foot and 12 foot pressurized tunnel, which was pretty neat. The entire circuit of the tunnel was under pressure, which allowed simulations of much higher airspeeds than were possible in a regular wind tunnel. It too had a circular cross section, and I thought this "stargate" was it when I first saw it.