The idea of establishing a Core Europe emerged as the membership of the EU grew beyond the original group of six member states. Its first prominent expression was the Schāuble-Lamers paper of 1994, envisaging the creation of a Kerneuropa of five or six states. It was reinvigorated at regular intervals ever since. These ideas were usually not accompanied by concrete institutional designs. It is unclear whether the euro area countries (or any subgroup within the euro area) have sufficiently homogenous policy preferences to justify the creation of a Core Europe. Yet, this idea keeps emerging in the discussions on the future of Europe. The paper describes this political trajectory and focuses on the legal feasibility of moving towards some form of Core Europe. It argues that the enhanced cooperation mechanism is not a suitable tool for its creation, but that the conclusion of international agreements might serve for the formation of a core Europe with a modest range of policy goals.