Wisconsin’s largest city, Milwaukee, is home to a decent handful of architectural landmarks: the Quadracci Pavilion, Santiago Calatrava’s postmodern lakefront stunner at the Milwaukee Art Museum; the Flemish Renaissance City Hall building, once the tallest habitable edifice in the United States; the Allen-Bradley Clock Tower, home to the erstwhile largest four-faced clock in the world; the Frank Lloyd Wright-designed duplexes of Burnham Street Historic District; and the Wisconsin Gas Building, a classic Art Deco skyscraper topped with an LED weather flame.

None of these buildings, however, have the ability to stop out-of-towners in their tracks (sorry, Calatrava) quite like the Mitchell Park Horticultural Conservatory — or, as native Milwaukeeans simply call it, “The Domes.”

Heralded as “Milwaukee’s Living Landmark,” the conservatory and its trio of massive, beehive-shaped glass domes — the Desert Dome, Tropical Dome and the Floral Show Dome — is one of the most distinctive works of midcentury modern architecture in Brew City, if not in the entire Midwest. In fact, the domes, each soaring 85 feet high and measuring 140 feet in diameter, are the world’s first conodial (cone-shaped) dome structures. Nearly 50 years after their completion, the trio of plant-housing glass bubbles remain the world’s only conodial botanical conservatories — a true feat of modern engineering.

Considering its status as a regionally iconic landmark and much beloved local institution of Milwaukee’s south side, it’s somewhat surprising to learn that the Mitchell Park Horticultural Conservancy appeared on this year’s list of America’s 11 Most Endangered Historic Places as identified by the National Trust for Historic Preservation. As it turns out, just like the prized specimens that they contain, the aging glass and concrete conservatories are also extremely fragile.

As detailed by the National Trust, the deteriorating domes were closed to the public this past February due to structural concerns and evidence of falling concrete debris in the Desert Dome. While the Desert Dome is slated to reopen soon — this weekend, in fact — following months of repairs and the installation of protective stainless steel netting, a permanent fix for all three structures has yet to be agreed on.

Mitchell Park Horticultural Conservatory, Milwaukee Considered a feat of modern engineering, Milwaukee's most bulbous architectural landmark is feeling the stress of old age. (Photo: Mark Baylor/flickr)

As Sandy Folaron, horticultural services director with the conservatory, tells WTMJ-TV: “This is not a long-term solution. Even a small chip falling from seven stories high can have an impact certainly on people, but also on the plants that are in here.”

So now comes the hard part: discussing the future. And this includes mulling over the dreaded “D” word: demolition.

County officials — Mitchell Park Horticultural Conservatory is operated by the Milwaukee County Parks system — obviously don’t want to be forced to raze the entire complex and build anew. However, they are facing an estimated $70 million repair bill to truly bring the Domes up to structural snuff. Starting from scratch might, in the end, be the more sensible use of taxpayer dollars.

And this is where the National Trust steps in.

While inclusion on the annual (28 years and running) Most Endangered Historic Places list may be viewed as ominously discouraging, a formal death knell of sorts, it’s actually a good thing — scary but ultimately good. After all, it’s usually the places that don’t appear that are most at risk. The list itself is meant to be catalytic, raising awareness and spurring action. With only a small few examples of endangered historic places that ultimately didn’t make it, the list is also extremely effective. To date, the National Trust has identified 270 endangered sites. While many are still under threat, less than five percent of them have been destroyed, demolished, suffered irreparable damage and decay or been lost to unchecked development.

This all said, the chances of the Mitchell Park Conservatory’s landmark domes sticking around for the long haul are good. But immediate action from the community is compulsory.

Mitchell Park Horticultural Conservatory, Milwaukee Mitchell Park Conservatory's three landmark domes house three distinct plant collections. (Photo: James Jordan/flickr)

Says Stephanie Meeks, president and CEO of the National Trust, of the situation in Milwaukee: “Rather than needlessly sacrifice this unique national treasure, local leaders owe it to the public to continue to explore a solution that preserves the Domes for the benefit and enjoyment of future generations.”

Just as the Desert Dome is about to reopen after extensive repair work, Milwaukee County has initiated a year-long planning process to consider viable next steps. As noted by the National Trust, local supporters of the conservatory are “advocating that this process be community-based, transparent, and fully explore all alternatives that would preserve the Domes.”

“Can it be restored? Should we talk about a new conservatory? Should we talk about a combination?” Folaron asks.

The National Trust wants to ensure that Milwaukeeans who value and patronize the craziest looking hot houses in all the Midwest play a role in addressing these important questions.

Sporting a footprint of 45,000 square feet and a total price tag of $4.5 million, the Mitchell Park Horticultural Conservancy, although not completed until 1967, was dedicated in 1965 by sitting FLOTUS Lady Bird Johnson. According to the Milwaukee Journal Sentinel, she called the Domes an “exciting new dimension in dramatizing nature for the people of Milwaukee and their visitors all year round.”

Trains at Mitchell Park Conservatory, Milwaukee Plants, schmants: Model trains in the Flower Show Dome are a hit with both kids and hobbyists. (Photo: Mark Baylor/flickr)

The Domes were built to replace the old Mitchell Park Horticultural Conservancy, a grand Victorian hot house built in 1898 that served as the dazzling centerpiece of the county park system until it, like the current conservatory, began falling apart.

Designed by Milwaukee-based architect Donald L. Grieb, the conservatory’s singular look was directly inspired by polymath futurist/architect Buckminster Fuller’s signature geodesic domes. Grieb even reached out to Fuller in hopes of a potential collaboration. “I asked them if they’d like to join hands with me in designing these domes,” recalled Grieb, then in his 90s, to the Shepherd Express in 2008. “They sent an attorney out and he made it clear their system was one they didn’t want to work on with another architect. So they were off the list.”

While the vast botanical collection housed within the three domes is no doubt the star attraction, an eye-popping LED lighting system installed in 2008 gained the conservatory a whole new generation of fans with decidedly shorter attention spans. Because if you can’t sell your antsy kids on cacti and tropical vegetation, a snazzy light show set to "Bohemian Rhapsody" should do the trick.

Other under-threat historic and cultural sites that joined Milwaukee’s iconic Domes on the National Trust’s 2016 list include Louisiana’s legendary Delta Queen steamboat; the Lions Municipal Golf Course in Austin, Texas, which was the first desegregated golf course in the South; the historic downtown district of Flemington, New Jersey; the highly photogenic Sunshine Mile retail strip in Tucson, Arizona; and San Francisco’s earthquake- and sea level rise-vulnerable Embarcadero.

As noted by the Journal Sentinel, this is the second time that a site in Milwaukee has appeared on the Most Endangered Historic Places list. In 2011, the Milwaukee VA Soldiers Home, one of the oldest surviving military veteran retirement homes in the nation, made the cut due to the fact that several of the complex's largest and most historically significant buildings (together, they comprise a National Historic Landmark District) had all but been forsaken and left to rot. Today, there's a firm plan underway to protect and restore them.

Matt Hickman ( @mattyhick ) writes about design, architecture and the intersection between the natural world and the built environment.