Classic tourist traps clutter Niagara Falls. They peddle boat and helicopter rides, elevator trips up tall view towers, bars, hotels and a Ripley's Believe It or Not museum.

In contrast at Igauzu Falls on the Brazil-Argentina border, the surrounding tropical forests are national parks. Only a few hotels have been allowed, and at a distance. Visitors hike trails to see the falls in their natural jungle. Arguments now rage whether a proposed theater and hotel at the entrance to Zion National Park would be akin to Niagara's tourist traps, or the beauty-preserving hotels nestled near Iguazu.

That battle is just another in a decades-long war over where to draw the line between protecting national parks' beauty and allowing development.

It has ranged from stopping a shopping center last year near Manassas Battlefield, Va., to attempts in Congress to limit development outside national parks to protect "scenic vistas."

The federal government technically has no jurisdiction in the latest battle near Zion. World Odyssey, Inc., wants to build a giant-screen, IMAX-like theater to show tourists a movie about the park. It also plans an 80-room hotel and a 275-space parking lot on 11 acres of private ground at the park entrance.

The nearby town of Springdale has jurisdiction over zoning and has scheduled a hearing on the matter Thursday. Town leaders strongly favor the project and hope it will boost the economy.

Opposing it are 20 environmental groups, who asked the government to buy the land - but suggested a price 50 percent lower than what owners paid for it years ago. The landowners say they are committed to the theater project.

Also, Rep. Wayne Owens, D-Utah, has been gathering signatures from members of the House Interior Committee vowing to oppose the theater with all their power. Rep. Jim Hansen, R-Utah, condemned that and said Springdale alone should decide the theater's fate.

Zion Superintendent Harold L. Grafe has told the press he doesn't oppose the project, just the site. Still, he said, "This outfit is trying to do things in an environmentally sensitive way, and if they were stopped, it's still private property. There could be something really gaudy put there."

On other fronts of the war nationwide, even what would likely be tasteful developments in or near parks have often lost.

For example, few tourists are likely offended by lodges at Bryce Canyon and Zion. But pressure groups in the mid-1970s almost forced their closure. And concessions at Cedar Breaks National Monument were closed, said Allen T. Howe, a former Utah congressman who lobbies for the National Park Concessionaires Association.

And newer parks - such as Utah's Canyonlands - do not have such facilities, even though Howe said they were envisioned in hearings when the park was created in 1964. In fact, the park's permanent visitors' center in the Needles District is only now being built - 27 years after the park was established.

National Park Service spokesman Duncan Morrow said the service has not allowed concessions in newer parks created since the late 1960s, and allowed only two new campgrounds after long environmental review and battles for tight funds.

He said the park service decided that in the modern world, tourists are easily able to obtain lodging and other services outside most new parks - so parks are maintained as naturally as possible. Visitors centers are constructed, however.

About land outside the parks, perennial fights occur in Congress about whether to limit development to protect scenic vistas. That slowed and eventually killed development of the Alton coal fields near Bryce Canyon. And it led many to oppose upgrading Dinosaur National Monument to a national park, fearing that might lead to more restrictions nearby.

The latest round in those running congressional battles came last year. Environmental groups sought creation of 120 new national parks and expansion of 178 existing parks to protect scenic vistas. That could have increased Park Service acreage eightfold in Utah.

Hansen called that a thinly veiled attempt to protect parks at the expense of ranchers, miners and others. He fought the proposal, resulting in a compromise bill creating a three-year study on guidelines for expanding park boundaries.

Until such guidelines are agreed upon - and probably even afterward - battles will still rage.

After all, one man's scenic vista is just another man's wasted economic opportunity. And tourists still flock to both Niagara and Iguazu - with their vastly different levels of protection. And both are still considered great natural wonders.