Mega-developer Forest City was not interested in preserving historic architecture as it built out its new-urbanist fantasy on the site of the old Stapleton airport. But that put Forest City on a collision course with preservationists over the fate of Hangar #61, which was designed by the premier mid-century architectural firm of Fisher, Fisher and Davis. Constructed in 1959 to shelter the corporate plane of the Ideal Basic Cement Company, the little hangar is an expressionist wonder, with a set of four intersecting hyperbolic arches carried out in thin-shell concrete. And now future generations will be able to enjoy it, because at the end of last year — and after years of efforts spearheaded by artist David Walter — Colorado Preservation took over ownership of the building with the promise to stabilize it and to find the best future use for it.