The Eiffel tower sex position involves three people. It can be a combination of two men one woman, one man two women, or other gender combinations preferred by the participant. But the most famous combination is one woman and two men.
This position is performed by having the two men stand facing each other, with a woman between them who is down on her hands and knees. One man enters her from behind, either into her vagina or the anus. While the woman is fucked by the one man, she is performing oral sex to the other man. And then the two standing men happily high-five one another, which creates a form of an Eiffel tower.
The two men can exchange positions later on. Or the woman can simply reverse her position. This position is no doubt a great three-some position where no one is left out in the game.