Walk along Berlin's quiet Greifenhagener Strasse in Prenzlauer Berg and you'll pass at least three of the city's hottest sex clubs - only you probably wouldn't know it from the look of them. You might not even know if you stepped inside.

Technically, these aren't sex clubs at all. These are Berlin's men-only darkroom bars. Like any other gay bar, men can grab a beer and cruise the scene at the relaxed front bar. But just a few meters to the back, men can fuck and suck in the dark without the fear of being judged or worse.

Since the gay rights movement of the 80s, and the abolition of Germany's anti-sodomy law Paragraph 175 of the Constitution, Germany has come a particularly long way integrating gay life into the fabric of the community. That darkroom bars are such an acceptable part of the landscape is what make cities like Berlin and Amsterdam unlike any other place in the world.

Says one darkroom frequenter: "In a place like London or New York, you can find these places but you kind of have to know where you're going; whereas here they are socially accepted and integrated into the gay scene [...], even into the straight scene. In Berlin, you can even find mixed [gender] darkrooms."

Darkroom bars bridge the divide between sex clubs and "normal" bars, blurring the lines between public and private spaces for sex. In effect, their visibility may be the sign of a community that doesn't stigmatize sexual exploration within or outside of queer life.

Darkroom bars are different from sex clubs because at a sex club, visitors immediately take off all or most of their clothes upon entering; sex is acceptable anywhere in the club, and most of the guests are there specifically to have sex. At most darkroom bars, a man can hang out all night fully clothed at the bar and never step foot into the darkness. But once he does, the darkness may set him looser than in an open sex club. Or, he can simply watch.

Like sex clubs, many darkroom bars have sex parties or fetish theme nights, and some of them have dress codes. Stahlrohr Bar, for example, offers a "Youngster Sex Party" for young men between the ages 18 and 28, "Fist & Fuck!" Sundays and "Sneakers, Boots & Socks" nights. The Midnight Sun offers the Golden Dreams party on Saturdays. The typical dress code is underwear, naked or fetish. During some sex parties, doors are locked for the entire party for about two hours so that the community is fixed and more private.

The darkroom itself is a maze of thin black walls, each room growing darker. Wooden stalls offer nooks of privacy and some are equipped with glory holes, transforming body parts into offerings for an anonymous guest in the adjacent stall. Used paper towels littering the floor and white T-shirts of waiting men are illuminated by the black light, but the farthest rooms - the ones with the slings - are pitch black.

One unspoken rule is no talking allowed. Says one source, "It's all in the eye signals - who you follow, who will follow you ... You don't get trained in darkroom etiquette, but all of a sudden you understand it. You get the opportunity to look people in the eye and the signals are clear."

Subtle signals are integral to the trick of finding like-minded partners in the dark. Handkerchief codes, for example, can be used to alert potential partners to various fetishes. The website of one Berlin darkroom bar lists over 27 shades of handkerchiefs, the right pocket implying a passive role and the left pocket implying an active one, like I am master/I am slave or I fist/I want to be fisted dichotomies. A dark red handkerchief in the left pocket signals I like to ride. In the right, it's I'm a pony.

Sometimes it's entirely in the details. While starting to decrease in popularity, the skinhead fetish (half dark denim, half acid-washed jeans and short-cropped hair) has been popular for several years. A "real" skinhead is distinguished from his look-a-like merely by the color of his shoelaces.

One fetish scene that inevitably draws attention to itself is the bareback scene. Some clubs have signed the Deutsche AIDS-Hilfe, an agreement that they will provide free condoms and lube behind the bar, but beyond that clubs aren't responsible. One club owner says, "We encourage everyone to have safe sex, but we don't go in and actually regulate. If two consenting adults want to have sex without a condom, that's not the business of the bar."

The impression of several visitors is that many men do not use condoms, especially during oral sex. "I don't think [darkrooms] are safe at all. I'm sure it's not all with condoms. There are a lot of people who go there very drunk or off their heads on drugs," says one.

While the owner of The Midnight Sun admitted that Berlin has a rapidly growing number of STD cases, "we see in the morning that a lot of people are using condoms ... they litter the floor ... especially in the last six months."

Whatever the statistics, Berlin clubs make it a priority not to stigmatize anyone with STDs. Several advertise "Positives Welcome." One club owner feels, however, that such ads stigmatize more than not. "I don't like such signs. Everyone knows that positives are welcome. I know a lot of people with HIV, some I've known for 15 years. They are human. Everyone is welcome here. Besides, there are a lot of other diseases that are just as serious: Tripper, Syphilis."

But the risk of STDs isn't the only reason why darkrooms are viewed by some men as unsafe. One visitor feels that darkrooms are potentially dangerous emotional-wise because so little communication occurs. "You have married or straight guys that are curious about gay sex and don't have to talk about it ... that's not exactly healthy."

Others feel this is precisely what makes darkrooms so safe: they are male private spaces free from the judgmental eyes of the public. There are no misconceptions about one's presence, communication is direct and sexual participation is not assumed.

As one man put it, "A private space is a place where there are no prying eyes of the uninitiated. And in this case, the uninitiated are 1) females and 2) heterosexuals ... In public spaces, especially in America, you define yourself according to how people see you, judge you. So if a nonmember shows up in a private space, it's as though the judgmental eye of society just came in, and all of a sudden men are pulling up their pants."

So how private are men's only darkrooms, and who is and is not a member?

The owner at The Midnight Sun says that on a busy night, 10 to 25 people will be turned away based on whether or not they'll "fit" with the rest of the bar. "If the crowd is between 30 and 45 years old and someone walks in who is about 18, we will refuse them."

Women are never allowed. Neither male-identified females nor drag queens are permitted to enter. If a woman is let in as an exception, she can hang out at the bar but is forbidden from entering the darkroom itself.

But in an age when gender lines are increasingly blurry, and in a city with such a large transsexual population, barring anyone at the door has some theoretical problems. A few men were willing to speculate on how they would react were they to be confronted in the dark by something "other" than a penis.

"I suppose if a woman showed up I would be a bit turned off ... or embarrassed. It would be almost as if you were getting a blowjob and your mom showed up," said one visitor.

Another said: "It's hard to imagine! I mean, it might have already happened to me. Sometimes people do just want to suck you off. So, you might not know."

While questions of gender definition may be another hurdle for darkrooms to tackle, the fact that men are able to talk about them with relative ease signals that Berlin is one city that's not willing to keep kinky sex completely in the dark.