In case any municipality shall have heretofore acquired or shall hereafter acquire by purchase, gift, devise, dedication or otherwise any lands or property for the purposes of a public park and place of public resort for recreation to be kept and remain open and unobstructed as a public park, it may erect or permit to be erected upon any part of the lands of such park not needed for a public park and place of public recreation a memorial building or buildings to be used for public uses and purposes. The ordinance or resolution of the governing body providing therefor shall, before it becomes effective, be submitted to the legal voters of the municipality for their approval, at a special election to be held for that purpose.