In his autobiography, Nikola Tesla mentions that he got received "a castle in Spain" as a reward for doing a good job while working in Europe. Are there any historical records of such castle or of Nikola selling it before traveling to the US?
"A castle in Spain" is a figure of speech in English. It means a non-existent reward, a fabulation, vapour, etc. In Spain we would say "castillos en el aire" (castles in the air) or "pueblos en Francia" (villages in France).