Simplify the following text for a Grade 5 native English-speaking person.
Original: Miskolc was elevated to the rank of oppidum ( market town ) in 1365 by King Louis I. He also had the castle of the nearby town DiÃ sgyÅ ` r ( now a district of Miskolc ) transformed into a Gothic fortress .
Simplified: Miskolc became a center of iron industry . In 1945 Miskolc and DiÃ sgyÅ ` r became one city .