The Secretary of the Interior is further authorized, by and with the advice of the National Commission of Fine Arts, to authorize and permit the erection in said memorial park of suitable memorials in harmony with the monument and/or memorial herein authorized that may be desired to be constructed by Spanish War organizations, States, and/or foreign governments: Provided, That the design and location of such memorials must be approved by the Secretary of the Interior, by and with the advice of the National Commission of Fine Arts, before construction is undertaken.