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Sex has long been for sale in New York City. But not until this weekend could you pay for it in a museum.

The nation's first Museum of Sex opens in Manhattan on Saturday with NYC Sex: How New York City Transformed Sex in America. But the debut exhibit may not be exactly what some people hope -- or fear -- it will be.

"We consider ourselves to be the first real sex museum in the world," explained MoSex Executive Director Daniel Gluck. "There are erotic museums in Europe, but they're not very serious. With so much great scholarship out there, we wondered why there were no forums, no museums doing exhibitions."

The museum offers memorabilia, including pornographic materials, documenting how prostitution, strip shows, fetish and homosexual subcultures got started in New York City. The exhibit also looks at a variety of health-related sex issues including abortion, venereal disease and the AIDS epidemic.

The museum's artifacts are generally presented in an academic, historical manner -- and visitors to the museum must be at least 18 years old to enter. But critics aren't buying it.

"MoSex is a Museum of Smut that uses its Ph.D.-educated staff as a cover for its libertine edge," said Dr. William Donohue, president of the Catholic League for Religious and Civil Rights.

"It's a good example of defining freedom as genital liberation, which is a problem in our society," Donohue told Foxnews.com. "It's totally irresponsible: Sexual recklessness results in out-of-wedlock birth, disease and death."

Donohue isn't the only critic. Executive Curator Grady Turner said the New York State Board of Regents felt the museum's proposed name (The Museum of Sex) made a mockery of the word museum.

"Eventually we kept the name and went private," Turner said.

Regents spokesman Tom Dunne confirmed MoSex had made inquiries about a charter and later withdrew its application. He said he did not know the source of the "mockery" quote.

Gluck said it's this sort of conflict that led to the museum's decision not to press for public funding. "Now we don't have to worry about the Catholic League or other conservative groups complaining about taxpayer dollars," he said.

But the lack of government money makes for a rather pricey entry fee, which, at $17, is considerably more than the unspecified donation policy common at many New York museums. MoSex will donate a portion of ticket proceeds to ACRIA (The AIDS Community Research Initiative of America), the Lesbian Herstory Archives and The Kinsey Institute for Research in Sex, Gender and Reproduction.

There's more to come for the museum, which will soon feature net-covered "ribs" on its façade meant to simulate the human form. Gluck says future exhibits may focus on sex in the Middle East and in South American cultures. There also might be an erotic art exhibit.

All of this sounds interesting to California research assistant and New York native Emily Gordon, 24, who said she'll try to check out MoSex next time she's in town.

"It's interesting to look at sex from a historical perspective," she said.

But English psychologist Jonathan Jackson, 28, said he'd sooner return to the ham museums of Madrid than spend $17 on the show.

"I've been to the sex museums in Paris and Amsterdam -- they were pretty boring," he said.