Finally - and following the wise advises of j5boul I visited Le Cocq, swinger club near Frankfurt, more preciselly in the city of Wordstat, about 600 km from Frankfurt.
Here is my report:
1. You need a car to go to Le Cocq. Definitively. It is in a very hidden place and there is no way you catch a train. follow the instructions in the web page to go there.
2. The function began at 8 o'clock Pm and at that time I was in. contrary to what j5boul told me there was no need to make a phone call. Perhaps because it was a friday. Perhaps is differente in saturdays.
3. The place is great. The house is very big and comfortable. All is as you can see in the photos in the web page, but bigger than what you probably imagine. There is a bar, a place to eat, changing boxes (mixed for man and women), a torture chamber, a swimming pool, bathes, and in the second floor is where action takers place. A lot of "collective" beds in some more or less engightened rooms whith a lot of wholes from where you can see the action. some rooms are less discrete than others. The whole club is very clean and there are a lot of condoms everywhere.
4. You can drink and eat what you can. It is all inclusive. I didn't drink alcohol because I had to drive.
5. the reception crew and the girl in the bar speak english, but it is a problem if you don't speak deutsche, because it is very difficult to join a conversation, specially if you come as a single.
6. The people. few people. No more than ten or twelve couples, four or five single guys and one single girl. They seem fewer because the house is very big. some of the people were under 30, most of them were in their forties.
7. the dresses. great variety. men, most of them only with boxers or slips. women in two plieces, some of them in a more sophisticated erotic costumes.
8. As the house is big and the people few there is a sensation of "subutilization" of the facilities. I didn't see people in the swimming pool or in the torture chamber.
9. The action. I sat in the bar and asked for an orange juice (!!!!) and began to explore the people. People chatted and drank. In one moment I saw the only single woman (a blonde, rather fat but with a very beautiful ass, face and tits) making some physical contact with one of the single boys (that is touching hands, etc.).I walked and walked around and I saw no action until I decided to go upstairs. In one of the rooms there was the blonde with the single man doing it. Some people were watching at them. Some people tryied to touch the woman. some were masturbating. I put myself behind one of the walls, with my hands and cock in a hole. the blonde touched my cock and began to masturbate me. I introduced my hand in a hole and touched her. Then I went to the room and entered it. in this moment arrived a couple: a woman and a fat man that began to play with the blonde, who had finished with the single man. I joined the group and the blonde said us to go to another bigger room. In this room the blonde began to suck the other woman's pussy. A lot of shouts and pleasure expressions. The fat man put behind the blonde and began to fuck her. I tried my best and put the blonde's hand in my cocq and touched her tits, etc. I try also to touch the other woman?s tits but she gently put my hand appart. The same did to another person. She was only interesteed in the blonde. When his husband, the fat man, finished I took his place and fucked her. It was a great time. When I ifinished I noticed that a lot of people were watching me and her.
Then washed and went to the bar, refill energy eating and began to watch the place again. .
Well, there was a lot of action then. Most by couples, single men didn't entered in it. most of the couples didn''t allow it. A lot of exhibitionism, for example a young couple were making love for about 45 minutes not allowing anyone to join (not even another couples). I saw a couple that only watched. Then there was a big happening: three couples mixed in one of the rooms. I saw again the blonde in this room.
after one or two hours of watching and eating I decided to go again for action. People were more calmed. All the couples have already fucked and were relaxing, chatting, etc. I saw the blonde again. She was with the dj, she was with her tits uncovered. For some of her movemens I noticed that she was part of the house crew. i think her function was to satisfy alone people in order that everyone feel good. I saw this policy in other swinger clubs: between the "real" swingers there is one or two women that do this job. Never mind. I asked her again and we went easily upstairs. We fucked and I came between her tits. A single man were masturbating behind us and when we finished asked her to fuck her. He was going to do it but she stopped him: He had to wash her tits because I filled her with my semen.
10. As a result it was a good experience, but if you are a single man don't expect to score unless there is a woman like this blonde, who, I guess works for Le cocq. But the experience is very good. don't hestitate and go when you are in frankfurt.
11. prices 130 the fee plus 70 renting a car (euros). It is expensive, but...
12 thank you very much to j5boul for your advises and information