Many people travel to Chile or Argentina for the breathtaking natural beauty of Patagonia. That’s why I went earlier this year. But there is another reason for a journey to the foot of South America — to relearn how to build and sustain great cities.

On our way home, my brother and I booked a night in a small hotel in an old section of Santiago. Our plane arrived in the morning, so we had time to wander around the city, across the very muddy Mapocho River, and over to the grand Plaza de Armas.

The Bellavista neighborhood surrounding our hotel, at the base of a mountain called San Cristobal, is filled with tattoo parlors and auto repair shops.

Side by side with the parlors and shops are local restaurants and bars, hostels and night clubs, and Pablo Neruda’s home, which is now a museum honoring one of Chile’s national heroes. The neighborhood is undergoing a rapid and healthy transformation.

The changes in Bellavista parallel the changes in Brooklyn, N.Y., in Charleston around the Crosstown, and in dozens of other cities in the U.S. that have experienced “urban revivals.”

What makes this organic transformation possible? Why do some places evolve so naturally from one era to another, seamlessly accommodating new uses and activities — Brooklyn and downtown Charleston, for example, and neighborhoods like Avondale and Wagener Terrace — while other places struggle, often unsuccessfully, to avert decline and abandonment, expending years and vast amounts of civic energy on community planning, economic studies and, occasionally, substantial investment in new infrastructure like bike lanes, medians and street trees?

The answer is far less complicated than most people imagine. Neighborhoods built on a network of connected streets can evolve and adapt, decade after decade and century after century. The converse is also true. Neighborhoods designed around a series of cul-de-sacs feeding into large arterial roads are almost destined to obsolescence and decline within a few generations. The single most important characteristic of a successful city is the street network.

But here is the disturbing reality. Most cities in America have spent the last century regulating the wrong things — lot sizes, building setbacks, parking requirements, land uses (residential, office, retail or industrial) — while ignoring the only thing that really matters in the long run: the street grid.

None of this is particularly new, nor is it rocket science. Urban planners and reformers like Andres Duany, Peter Calthorpe and James Kunstler have lectured and written about it for decades. And they learned the importance of the grid from early 20th century writers like Lewis Mumford (“The City in History”) and Jane Jacobs (“The Death and Life of Great American Cities”).

So, to paraphrase former New York Mayor Ed Koch, “How are we doing?”

The answer here in Charleston —the city whose historic downtown is a national icon for beautiful, efficient urban design — can be summed up in one word: terribly.

Ed Buckley’s column last month provided a succinct description of the unfolding disaster that is Johns Island. Here is one example:

“The residents of Coral Reef Drive on Johns Island live about 1,000 feet from the Tattooed Moose, which is a pretty great place to grab dinner and spend a night out. At a leisurely pace, they could walk that distance in less than four minutes.

“But there’s no way to get there directly. Instead, a pedestrian would have to walk three times as far through winding suburban roads.”

This dysfunction is not limited to Johns Island. Here’s Ed’s observation of West Ashley:

“Students could theoretically walk about 1,600 feet from Conservancy Lane to West Ashley High School, but it’s an incredible 7 miles to get there on main roads, or about 3 miles to get there by cutting through neighboring subdivisions.”

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It’s not like we didn’t know this would happen. The Conservation League funded a transportation plan for the Maybank Highway corridor 10 years ago that included the “pitchfork” proposal to distribute traffic along Maybank before it reached the choke point at River Road.

The plan also recommended constructing new roads parallel to Maybank, between River Road and Main Road, and River and Bohicket roads, with “additional cross connections between the primary arteries to increase capacity of the road system.” (Hall Planning and Engineering Study, 2008) These would allow residents to travel shorter distances from their homes to the Tattooed Moose and other nearby destinations, and to walk or bike safely without having to travel on Maybank.

The city has negotiated a few connections between subdivisions along the corridor but, as Ed points out, the result is anything but a genuine street grid that would allow walking, biking and short car trips. As of the past few weeks, even the completion of the pitchfork is in doubt.

There is still time to implement this tried and true approach to growth, to pull Johns Island away from the precipice of total gridlock. While the threat of political meddling and backroom dealing is ongoing and real, the citizens who have persistently called for reforms and a moratorium on growth can insist on these essential improvements.

As the city of Charleston expands its urban footprint, it owes the residents of Johns Island better. All the know-how, tools and plans are there, ready to be implemented. Now is the time for residents to hold planners and leaders accountable.

We must demand that our neighborhoods be designed — like Santiago’s Bellavista and Charleston’s historic peninsula — with the bone structure to thrive and to evolve and adapt over the coming centuries.

Dana Beach is founder and director emeritus of the Coastal Conservation League.