Hundreds of migrants storming into Spain’s North African enclave of Ceuta have exposed one of Europe’s most unusual borders. Situated on the African continent but governed by Spain, Ceuta and Melilla form the European Union’s only land frontier with Africa. As migrants crossed by land and sea, overwhelming security forces and straining detention centres, the crisis reignited debate over immigration, border control and Europe’s vulnerability to fresh migration surges across the Schengen zone.