The largest public-private partnership investment in a national park is delivering a new experience for visitors to the landmark Gateway Arch in St. Louis, which was designed by the late-architect Eero Saarinen. The 10-year path to the opening this month was full of hurdles, including floods. And the project’s 46,000-sq-ft underground visitor center expansion needed to be built without shutting down the arch, which gets nearly 3 million visitors each year.

“They were looking for a kind of minimal impact on the landscape,” says Scott Newman, managing partner at Cooper Robertson. “We had to work with the Missouri State Historic Preservation Office to review proposals to make sure that we weren’t negatively impacting the historic resource.”

Read more at ENR.