ROTTERDAM -- A rebuilt New Orleans might contain dikes thick enough to double as parks and a futuristic zigzag-shaped building with hanging gardens to symbolize the city's rebirth after Hurricane Katrina.
These were among the ideas on display at a conference yesterday where dozens of architects, urban planners, and scholars sketched out their post-hurricane recovery visions.
Because of the similar engineering obstacles created by the low-lying Netherlands and the Louisiana delta, Tulane University and the Netherlands' Architectural Institute issued a joint challenge to the specialists to develop plans for rebuilding New Orleans.
''Gatherings like this allow us to begin to look at the whole range, from individual buildings, to larger symbolic buildings, to the landscape itself," said Reed Kroloff, dean of Tulane's School of Architecture.
He said many of the projects on display would likely never be built. ''They are intended as thought-provoking, visionary schemes," he said.
Design ideas will be on display in Rotterdam through March 6 and will then travel to Washington, New York, and eventually to New Orleans, though exact dates and venues haven't been scheduled.
Kroloff stressed that rebuilding New Orleans will require restoring trust in government and the involvement of the city's residents.
With this in mind, the Rotterdam firm MVRDV drew inspiration from a drawing made by a New Orleans elementary school girl of an imaginary hill that would have provided safety when her neighborhood flooded.
So the firm designed a hill, just across the freeway from the Superdome. It would contain an elementary school cradled in its heart.
''It could serve as a safe place when the city floods again, but it's also a little cynical, a reminder that it can happen again," said exhibition curator Emiliano Gandolfi. ''It's good to be critical, to remember that."
A joint plan by architects Hargreaves Associates of Cambridge, Mass., and West 8 of Rotterdam would use New Orleans's City Park as a recovery centerpiece.
First, fresh water would flow through the park to flush out salt water absorbed during post-Katrina flooding, and temporary housing would be set up on the park's west side to house residents as they return.
Then, as people moved out to new, permanent homes, the park would be used as a tree farm. When mature, some trees would be used to replace those lost in the city's destruction.
In the final stage, the park would go back to being just a park. But it would contain mini-river deltas capable of absorbing and pumping extra water out to sea in case the city floods again.
''The Ziggurat," a zigzag-shaped building resembling ancient stepped palaces, was designed by UN Studio of Amsterdam as a symbol of New Orleans' rebirth. The Ziggurat would house a media library, city offices, and a large auditorium, and have hanging gardens like those of ancient Babylon.
Tim Christ, from the Los Angeles firm Morphosis, called his team's plan ''a provocation." Asked to design a project for an iconic building, they proposed a radical refocus of the whole city, condensing it into the historical city center.
''There's not an architectural problem, the problem is displacement of people," Christ said.
''Logic dictates, there's no way to provide fire protection, police, teachers, schools, roads and street lights in all areas that were destroyed. There's no tax base to pay for it."
The Morphosis proposal would create a park in the lowest part of the new city center, and allow other low-lying areas outside the center to return to marshy delta. Houses built outside the approved zone, especially cheaply built houses built since the 1970s, would be left alone, vulnerable to future flooding and hurricane winds and impossible to insure.