These dreams range from the very-much-doable (Norman Foster extending Madison Square Park) to the interesting-but-unlikely (requiring the new super-tall apartment towers to provide public space) to the good-but-too-expensive (elevated bike lanes) to the insane (damming and draining the East River and using the riverbed as farmland) to why-aren’t-we-doing-this-already? (a “cultural Airbnb” offering vacant storefronts for temporary use as performance or art venues).