For $59.99, visitors can see the Statue of Liberty and get a ticket to the National September 11 Memorial as part of the NYC Freedom Tour.

For $10, tourists can join a walking tour of Lower Manhattan led by someone personallyaffected by the terrorist attacks.

Those seeking a less crowded space to reflect might wander along the Brooklyn Heights Promenade, where a faded black-and-white photograph nailed to the railing shows the view when the Twin Towers still stood.

The attacks left an indelible mark on New York City's tourism industry: The number of hotels downtown has tripled in the past decade, and the area attracted a record-breaking nine million visitors in 2010, according to the Downtown Alliance.

Many pilgrims say they want to pay their respects, pass on the story of what happened to their children, and try to make sense of what they witnessed that day.

But the surge of 9/11-related tourism has also raised prickly questions about how to market such destinations without appearing to exploit or diminish the tragedy. Tourism industry leaders and New Yorkers alike have grappled with the right balance for a decade, a task made even more urgent by the planned opening of the 9/11 Memorial to the public on Sept. 12.

'I think that for some reason calling it a tourist site does have some kind of negative connotation, but it's a reflection that a lot of people from all different walks of life want to come visit and want to come learn,' said Joe Daniels, President of the National September 11 Memorial & Museum. 'I would be very concerned if we didn't see this amount of interest -- if we were overestimating how much people cared about 9/11 and what happened on that day.'

That doesn't appear to be the case. More than 380,000 people have reserved passes to the Memorial since July 11. They come from all 50 states and 70 different countries.

The impulse to convert a family vacation into a pilgrimage to a site of tragedy is hardly new, said scholars who study the tourism industry. It even has a name: 'dark tourism.'

'The assumption fundamentally with tourism is that it's about escape, fun, leisure recreation,' said New York University professor Barbara Kirshenblatt-Gimblett, who has studied tourism for 30 years. With 'dark tourism, the sun went down. The lights went out,' she said, noting that motivations can range from the macabre to the moral.

In that sense, she said, '9/11 is no different from any number of sites in the world where something of cataclysmic importance happened and where there is a moral imperative to remember it, to commemorate it, to feel it.'

Still, some tours have refused to incorporate Ground Zero into their official routes.

'It was not appropriate to create a special tour to financially gain from this,' said David Chien, the director of marketing for Gray Line New York.

But, he noted, that will change with the opening of the Memorial to the public. For a $5 surcharge per person, groups of 10 or more -- and individuals, if there are extra tickets -- will be able to visit the memorial as part of the company's hop-on, hop-off bus tours.

Others had no such qualms: OnBoard Tours has started the NYC Freedom Tour ($59.99) for the tourist who wanted 'a general tour of the city, but also wants to see the hot new attraction, which is the brand new memorial,' said OnBoard Tours CEO Tom Schmidt.

He defended the tour against the charge of opportunism.

'Everyone that's in the tour business makes money by taking people places and showing them things,' he said, noting that tours in other cities include the Vietnam Veterans Memorial. 'It's not because we're trying to make money off disasters that occurred in wars, it's because we provide a service to take people to see things they want to see.'

He noted the company closes only one day a year: on Sept. 11.

The leaders at the WTC Tribute Center, a nonprofit run by the September 11th Families' Association, created a tour of downtownmemorials after watching people peer through the fence at Ground Zero.

'There was a hole in the ground and nobody here to tell anybody anything and it made no sense to us,' said Lee Ielpi, president of the September 11th Families' Association. His son Jonathan, a firefighter, died in the attacks.

In 2005, his organization started intimate walking tours led by people directly affected by the attacks. Guides might be a first responder who rushed to the site, a survivor who worked in one of the towers, or a family member who lost a loved one.

A year later, they opened the Tribute WTC Visitor Center. More than 2.3 million people have visited the center ($15 without the tour), Mr. Ielpi said, while more than 200,000 people have taken the tours ($20 for the package).