Taking the example of the Basel carnival Fasnacht, the paper shows in what way ritual can maintain the impression of being traditional and unchanging, and yet be open to changes and innovations. As the basic conceptual framework, we use the notion of liminality, which Victor Turner identified as the creative moment of ritual. In the Fasnacht this liminal dimension appears in two degrees. The carnival as such represents a reflexive liminal counterpart to the standard social structure, yet it is itself also highly structured and bound by conservative traditional rules. As a reaction to this, there arises within the Fasnacht a "second-degree" liminality in the form of the so-called wild Fasnacht, which turns the official antistructural Fasnacht rules upside down once again, testing their validity. While the carnival structure offers a regulated opportunity for questioning everyday social behaviour, wild Fasnacht questions even this regulated manner of questioning as such, opening space for its reflection and modification. We use detailed examples to demonstrate how the subtle dialectics of structure and antistructure keeps the tradition of Basel's Fasnacht alive and allows it to evolve without destroying its aura of traditionality.