When Philadelphia adopted a new zoning code last year, it was like opening a Monopoly box and finding only an instruction book inside. But now, the Nutter administration is finally ready to provide the city with the playing board and all the pieces.

Planners have just updated the zoning classifications for every block in greater Center City, from Girard Avenue to Washington, a task that took 16 months and required plenty of shoe leather. Out of that enormous undertaking has come a new, modern map that will dictate where buildings will go and, ultimately, how much properties will be worth in the densest, busiest, priciest part of the city.

Before the game can start, the Planning Commission and City Council must approve the new map. Given the recent pushback from Council over the new code, there is sure to be plenty of card swaps ahead. "We know this is controversial," planner Laura Spina acknowledges, "but we think it is worthy of conversation."

Spina, who oversaw the remapping for what's being called the "Central District," gave me an advance peek last week at the map and recommendations, which will be formally presented to the commission Tuesday. From what I saw, nothing terribly radical was proposed - unless you consider zoning that favors a dense, transit-oriented, tech-friendly, mixed-use downtown a radical notion.

Zoning, as devotees of another game, SimCity, know, is a tool to shape the contours of the skyline. As greater Center City has become an increasingly desirable place to live over the last 20 years, zoning officials have often handed out variances that allowed tall buildings to rise, seemingly at random, in the oddest places.

The new zoning map should end that free-for-all. If you look at the colorful mosaic of the Central District's zoning map, you'll see crimson in the center, yellow at the edges. The darkest crimson area - a stumpy cross with City Hall at its midpoint - represents the skyscraper zone. Yellow indicates the vast plain of rowhouses that fans out from Philadelphia's center.

The crimson fades to red at the edges of the cross - Race Street in the north, Walnut in the south - where tall buildings are still OK, just not those of skyscraper stature. Planners capped the towers' height at between 20 and 35 stories to encourage a wedding-cake profile for the skyline.

One reason for the stepping down is to ease the transition to the rowhouse neighborhoods. Washington Square West, a rowhouse area that maintains an uneasy relationship with Jefferson Hospital, will be a big beneficiary of the limits on behemoth towers.

Essentially, planners want to contain super-tall towers within a narrow band of the city where transit is strongest. Note, the word is contain, not limit. There are still plenty of sites where the next Comcast tower can find a home, should anyone still want to go that tall. But clustering skyscrapers makes a lot of sense because it prevents bizarre juxtapositions of scale.

The planners also hope the map will put an end to damaging speculation that lets land sit idle for decades while the owner waits for someone to build a 60-story tower in a neighborhood of rowhouses. As Spina noted, the outmoded zoning "puts a price on land that is not realistic."

Creating the new zoning map wasn't just about regulating the height of buildings, though. Philadelphia's land-use map is decades out of date. Neighborhoods that are mere blocks from Market Street's sleek skyscrapers are zoned for assembling locomotives. Broad Street, which should be Philadelphia's proudest boulevard, still allows strip malls and fast-food drive-ins. Developers who want to build a simple apartment building spend months petitioning for zoning changes.

Once the new map is approved, those industrial and auto-centric commercial uses will no longer be allowed in Center City. Imagine: no more stand-alone drugstores swimming in asphalt parking lots, breaking up the continuity of Spring Garden Street, Washington Avenue, Ridge Avenue and Broad Street.

The new map encourages mixed-use, mid-rise apartment houses on those wide streets, similar to the one going up now at 20th and Callowhill. The new classifications could make it possible someday - market willing - to transform Callowhill's garage row into a residential boulevard with parking as a mere side use.

The map represents a big, philosophical switch from the '60s. The east end of Spring Garden was intentionally zoned for manufacturing buildings, which drove out its once elegant townhouses. Now, planners want to remake the street to look like Northern Liberties - dominated by housing, but still capable of accommodating artisans and light manufacturing.

As part of the remapping, planners have put together a wish list of ideas to stimulate growth in the rezoned areas. Some have already received attention, like a Reading Viaduct park and a bus that would run the Reading trench, between the Art Museum and Center City.

For my money, the best idea in the plan is the creation of what I think of as the "vacancy sheriff": someone who would track down speculators who let buildings and retail spaces sit idle. The sheriff would work with the owners to bring the properties up to code and find tenants. The city also wants to hire an architect to manage changes to City Hall's historic spaces, and help enliven its courtyards with activities, such as cafes or kiosks.

As in Monopoly, the board alone isn't enough to persuade players to start buying properties and putting up houses. Fixing the tax and school systems is crucial.

Nor will the map achieve its potential if Council continues to hold tight to its prerogative to hand out variances to those with the loudest voices and fattest wallets. Give Mayor Nutter credit: Despite his administration's backsliding on projects like the Arch Street garage, this new zoning map embraces a progressive urban agenda.

Like an airbrushed photograph by a skilled artist, the new zoning map is an ideal that depicts Philadelphia's best self. If the map helps the city look a little more like that glamour shot, so much the better.

Contact Inga Saffron at 215-854-2213, isaffron@phillynews.com, or follow on Twitter @ingasaffron.