The construction of buildings is also subject to some regulation under the police power. The city is vested with authority to prescribe the strength and manner of constructing buildings, to define fire limits, and to pass and enforce all necessary police ordinances; and the power conferred upon it to pass “all necessary police ordinances” is construed as delegating to the city all the appropriate police power of the state.[77] No question is made but that the city council has power to regulate the height of buildings with a view to health and public safety; but it may be doubted whether the police power would justify the municipal authorities in imposing more rigorous restrictions upon the character of buildings to be constructed along boulevards and around parks than in other parts of the city. The Supreme Judicial Court of Massachusetts has sustained the right of the legislature to delegate to a city the power to regulate the height of buildings, to prescribe different regulations for different districts, and to invest a commission with the right to determine the boundaries between such districts,[78] and has expressed the opinion that certain special regulations of the height of buildings around a public square might be imposed under the police power without making compensation.[79] It is doubtful whether local distinctions of this character would be sustained in Chicago under existing legislation, except in so far as they might be justified by the power to establish fire limits. The legislature might delegate to city councils the power to district the city and prescribe different building limits in different districts; but any distinctions of this sort would have to rest upon real differences, and it remains doubtful whether the police power could be invoked to justify making a special district of the area surrounding a public square or avenue. The council could not be invested with authority to establish building lines without awarding compensation to the owner;[80] nor could the legislature confer the right to regulate arbitrarily the character of the business to be conducted in premises abutting on a boulevard.[81] A business which is an actual nuisance may be prohibited altogether; and the legal machinery exists for excluding saloons and some other kinds of business from limited areas. Such exercise of the police power must, however, bear some reasonable relation to the public health, safety, or morals, and could not, under existing constitutional restraints, be extended to business in general.