1. Introduction : seven types of ambiguity, c. 1100-c. 1500 / David Abulafia -- 2. Crossing the frontier of ninth-century Hispania / Ann Christys -- 3. Emperors and expansionism : from Rome to Middle Byzantium / Jonathan Shepard -- 4. Byzantium's eastern frontier in the tenth and eleventh centuries / Catherine Holmes -- 5. Were there borders and borderlines in the Middle Ages? The example of the Latin Kingdom of Jerusalem / Ronnie Ellenblum -- 6. Government and the indigenous in the Latin kingdom of Jerusalem / Jonathan Riley-Smith -- 7. Latins and Greeks on crusader Cyprus / Peter W. Edbury -- 8. Genuensis civitas in extremo Europae : Caffa from the fourteenth to the fifteenth century / Michel Balard -- 9. Granting power to enemy gods in the chronicles of the Baltic Crusades / Rasa Mazeika -- 10. The blue Baltic border of Denmark in the high middle ages : Danes, Wends and Saxo Grammaticus / Kurt Villads Jensen -- 11. Hungary, 'the gate of Christendom' / Nora Berend -- 12. Boundaries and men in Poland from the twelfth to the sixteenth century : the case of Masovia / Grzegorz Mysliwski -- 13. The frontiers of church reform in the British Isles, 1170-1230 / Brendan Smith -- 14. Neolithic meets medieval : first encounters in the Canary Islands / David Abulafia