Parts of Jakarta, Indonesia are sinking more quickly than Venice, and Reuters reports that the city has lost 13 feet of elevation over the past 30 years. That would be a huge problem even if Jakarta weren’t home to nearly ten million Indonesians. But there could be hope in store, reports Wendy Koch for National Geographic: The city is embarking on a plan to build a gargantuan bird-shaped seawall.

Koch writes that the city is in the midst of the first phase of a $40-billion plan to protect itself with a 25-mile-long, 80-foot-tall wall and a series of artificial islands shaped like a Garuda, a mythical bird that’s Indonesia’s national emblem.

On its website, the project’s Dutch design firm says that the Great Garuda seawall will take 30 to 40 years to complete. First, Jakarta’s current seawall will be reinforced and combined with water treatment projects. Then the Garuda-shaped seawall, complete with 17 artificial islands, will be constructed on the city's western side. Once finished, the islands will be home to an entirely new part of Jakarta expected to house hundreds of thousands of residents. Another seawall to the east, a new airport and a port expansion project will round out the construction.

There’s just one problem: Nobody’s sure if the project will actually be effective. Koch reports that experts are concerned that the wall will only treat the symptom—a sinking city—and not its cause, untrammeled development and a growing population that mistreats Jakarta’s water supplies.

Seawalls can be a tempting solution for cities desperate to keep the ocean out, but as Smithsonian.com reported earlier this year, they can have negative environmental impacts, too. By bouncing waves back into the ocean, seawalls can harm local wildlife, erode beaches and increase the impacts of storms.

Earlier this year, a study by Indonesia’s maritime affairs ministry warned that the Garuda wall would have exactly those effects. The Jakarta Post’s Corry Elyda reports that the wall could also displace tens of thousands of fishers. But other specialists disagree, saying that the project’s benefits outweigh its drawbacks. After all, the growing city has faced catastrophic flooding in the past and remains vulnerable to natural disasters in the future, something the seawall should help address.

No matter what its impact is on Jakarta’s environment, the Great Garuda will leave an indelible mark on the city itself. A website for the project notes that the bird is the first thing travelers will see when they come in for a landing over the Bay of Jakarta—an enormous avian structure that just might save its city with its ambitious wingspan.