If federal funds are available for reimbursement therefor, the department may acquire, either in fee or in any lesser estate or interest, real property adjacent to any highway included in the national system of interstate and defense highways or the federal-aid primary highway system, which the department considers necessary for the preservation, maintenance or conservation of scenic lands or areas adjacent to such highways or which it considers necessary to preserve, improve or enhance the scenic beauty of or points of interest in the lands or areas traversed by such highways. Nothing in this section shall authorize the use of eminent domain to acquire any dwelling or any building or other enclosure, and the appurtenances thereto, in which commercial activities are conducted.