A major West Coast city is planning to celebrate a world's fair anniversary by sprucing up a major cultural center that was the legacy of an exposition. Seattle in 2012? Yes, but also San Diego in 2015.

San Diego has hosted two world's fairs, both overshadowed by competition from more famous fairs in other cities. Still, the fairs of 1915-16 and 1935-36 left a legacy by dramatically enhancing Balboa Park, one of the largest urban parks in America, and at nearly a century-and-a-half old, one of the oldest public parks in the country. The park today appears to be at a kind of crossroads, quite literally, as the debate over its future includes who will take care of it, and whether to ban cars.

Balboa Park, a National Historic District, includes an amazing array of theaters, museums (17 by my count), and other public amenities, not the least of which is the famous San Diego Zoo, launched during the last year of the first expo. The grounds are spectacular, with botanical and desert gardens, and many of the incredible buildings and pavilions from both fairs continue to be used today. The landscaping is lovely, the long, shady colonnades reminiscent of Spain or old Mexico.

The architectural styles fit with their eras: The centerpiece is the old California Building with its dome and tower, which houses the Museum of Man anthropology exhibit. It has been described as "Mexican Ultra Baroque," and you can throw in a bit of Rococo too, featuring as it does figures of cherubs and explorers on its columns and elaborate church-like facade. Instead of saints, there are major figures in California history, including Serra, Portola and George Vancouver, of all people. How did a Brit rate? Vancouver was the first non-Spanish European to visit San Diego, it turns out, and reported back home that California was, in essence, ripe for the taking. His visit spurred the Spanish to take colonization there a bit more seriously.

Another section of the park features the 1930s buildings of the Depression-era expo, and their inspiration seems to range from Mayan to what you might call Pueblo-Deco. The short version is, it is extremely uncommon to see any site with so many world's fair buildings intact and in use, let alone where the basic plan of the fairs is visibly intact. Missing, of course, are some of the original attractions, such as the Zoro Gardens nudist colony. Gone too is the less-racy, mission-style Washington State Building from 1915.

Balboa Park is widely recognized as a civic gem. It is run by the city, but last fall the mayor declared that new leadership was needed in a time of diminished civic resources. So, a Balboa Park Conservancy has been created to spur private sector and nonprofit support for it, and a major plan is being crafted for a multimillion-dollar investment in its future. The catalyst isn't a new world's fair, but celebration of the 100th anniversary of the seminal 1915-16 Panama-California Exposition.

One bone of contention is a plan to make the park more pedestrian friendly. The center of the park is beautiful Plaza de Panama, surrounded by wonderful old buildings. But it is also filled with cars and buses, and some would like to see them cleared out. The 1915 fair included a major expansion of public transportation, and Balboa Park was served by new and innovative streetcars.

But while the pedestrian structure remains today, cars at times overwhelm the place. As I walked the grounds, I found way too many parking lots intruding. One question is whether to build a new parking garage, restrict vehicle access, or declare occasional car-free days. In a re-do at Golden Gate Park in San Francisco, a large parking garage was put underground. Can the park be de-carred without declaring a war on cars? (Here's how it might look. Be sure to watch long enough to see the image transform.) Preservationists and others have raised concerns about the proposal to build a bypass to steer cars into a new garage. As would be recognizable to anyone from Seattle, the process of making a decision has become controversial.

By way of comparing dilemmas, Seattle Center is a cultural nexus with an intact street grid, but few cars within the site. Balboa Park, on the other hand, is a space designed for pedestrians and is distinctly more park-like, but cars intrude more visibly. Too, amenities are more concentrated (imagine if the Burke Museum, Museum of History and Industry, SAM, the Museum of Flight, and the Woodland Park Zoo were all clustered at the Center too). Is the Plaza de Panama an urban space where cars fill the central square, or should it be a pedestrian plaza with cars excluded, buried, or limited to the periphery? That's part of shaping discussions about mobilizing money and support for a new and improved Balboa Park.

Wandering around, a Seattleite might be envious of Balboa's assets: the walkways, gardens, variety, and greenery. In the desert garden, you might see hummingbirds, tanagers, and a prairie falcon flitting among the cacti. Balboa is a much more pleasant stroll than Seattle Center, and much bigger too (1,200 acres vs. 74). There are food vendors and excellent eateries, notably Prado where I can enthusiastically recommend the Kobe beef sushi (unlike Center House fare). Once out of your car, you can access most of the amenities on foot, and one ticket will give you entrance to all the museums, which range from the San Diego Art Museum to museums devoted to cars, trains, sports, and natural history. There's a science center too.

On the flip side, the park is ringed with roadways that cut it off from the surrounding neighborhoods, and its location away from downtown and in the landing path of the airport add elements of isolation and noise.

The short of it is: No such center is without drawbacks, and they all seem to be a work in progress. And no major civic center, once created, is self-sustaining. Renewal, revival, and rethinking are part of the territory. Balboa Park is not a fly caught in amber, but it has changed — both for better and worse — with the times. One of its post-fair uses in the 1950s and '60s was as a city landfill, an area now needing expensive cleanup.

Still, many other cities should be so lucky to have such a legacy to work with, and to fight over.