We develop a model of competition between shopping centers, comparing competitive outcomes in three alternative modes of retail organization, namely: streets (in which neither developers or retailers internalize agglomeration effects between products); malls (in which developers internalize); and supermarkets (in which both developers and retailers internalize). For a fixed number of centers: (i) converting streets to malls intensifies developer (but not retailer) competition, which increases product range (i.e., the number of shops built by the developers) and consumer surplus, reduces profits, and has ambiguous effects on welfare; (ii) converting streets to supermarkets intensifies retailer and developer competition, has ambiguous effects on product range (number of shops), reduces profits, and increases social welfare. With free entry both conversions reduce the number of centers and, if there is excess entry, conversion to supermarkets (but not malls) unambiguously increases welfare.