They've been cropping up everywhere -- complexes that mix retail, offices and residences in a single project meant to serve as little downtowns. One's gone up in Englewood, and there's one at Lowry, one's under construction in Lakewood, and one's in the planning stages in Boulder. But architecturally, the pick of the litter of these mostly mundane prefab villages is the East 29th Avenue Town Center at Stapleton. This complex of substantial-looking neo-modernist buildings by Peter Dominick's Urban Design Group is laid out in a very formal, symmetrical arrangement in which every building is mirrored by an identical one. Taken all together, this center has plenty of curb appeal.