Cipangu was first mentioned in Europe in the accounts of Marco Polo. It appears for the first time on a European map with the Fra Mauro map in 1457, although it appears much earlier on Chinese and Korean maps such as the "Gangnido". Following the accounts of Marco Polo, Cipangu was thought to be fabulously rich in silver and gold, which in Medieval times was largely correct, owing to the volcanism of the islands and the possibility to access precious ores without resorting to (unavailable) deep-mining technologies.