The Council shall have the power to buy, sell, or exchange any real estate found necessary or convenient in the opening, construction, straightening, widening, or otherwise altering of any street, alley, or public way within the City; and by resolution and proper deed to convey to any person, firm, or corporation any land used heretofore or hereafter used, for street or other public purpose, when, in the judgment of the Council such land shall be no longer needed for such public use.