Brussels illustrates the paradoxical condition of a frontier city: simultaneously the capital of Belgium and the de facto capital of the European Union, it is marked by deep internal linguistic divisions while serving as a symbol of supranational unity. Historically situated between the Latin and Germanic worlds, Brussels reflects Joël Kotek’s concept of the frontier city defined by contested sovereignty, dual legitimacy, and persistent potential for conflict. The city’s universities, the Université libre de Bruxelles (ULB) and the Vrije Universiteit Brussel (VUB), illustrate how these frontiers are institutionalized. Founded as a single liberal and secular university in 1834, the institution was formally divided along linguistic lines in 1969, with each claiming continuity with the original foundation. The split mirrored Belgium’s federalization process and the consolidation of the language frontier fixed in 1962–63. Yet the ULB–VUB divide also generates opportunities for border-crossing collaboration. Joint initiatives, such as the Usquare.brussels project and the 2025 opening of a shared university building on the campus border, embody efforts to transform division into cooperation. These projects demonstrate how symbolic and institutional borders can function both as sites of separation and as bridges fostering integration. Brussels thus encapsulates Belgium’s broader condition: a bordered polity whose resilience lies in negotiated coexistence, making the city a microcosm of Europe’s ongoing struggle to reconcile unity with diversity.