What if there was a giant dome over Midtown Manhattan? A 108-story hyperbolic skyscraper in the place of Grand Central? Or a futuristic mini-city of 8,000 on Ellis Island?

These are some of the questions you ponder while browsing Greg Goldin and Sam Lubell's new book Never Built New York (Metropolis Books, $55.00), which examines some of the most outrageous architectural and urban planning ideas from more than 150 years of New York City history. The book features beautiful architectural sketches and renderings of these proposals, some of which seem like they would have been legitimately exciting, some of which are truly nightmarish, and some of which the creator was probably just fucking around with.

An elevated pneumatic railroad would have been cool, as would Steve Holl's prescient 1980 design that would have turned what is now the High Line into a long elevated complex of mixed-income housing units and a plan to build the world's largest park next to Floyd Bennett Field.

Some of the crazier ideas include Buckminster Fuller's proposal to put a dome over Midtown Manhattan and William Zeckendorf's scheme for a 144-square-block airport elevated above the West Side and jutting out into the Hudson River.

On the terrible ideas front, there are lots of starchitect boondoggles and mid-century plans to turn the entire city into highways, most notably those offered by Robert Moses.

Well-represented in the book are designs for projects that did get built, but by other architects or in radically revised form, such as Daniel Libeskind's asymmetric corkscrew World Trade Center concept and Frank Gehry's probably-would-have-had-a leaky-roof proposal for the Atlantic Yards. There is an entire chapter devoted to different iterations of the UN, one of which would have rammed it through much of Midtown East.

The book also offers an important reminder: Santiago Calatrava is the master of expensive, impractical, and bombastic architecture.