I Have a Bronze City

I have a bronze city that is warm in winter and cool in summer. There is a magical mineral vein in this world. So, science goes astray here... This is a world where machinery is king. There is no internal combustion engine, but the cars here do not run very slowly. There is no electricity, but the lights here are still bright at night. Bronze, silver, gold, platinum, diamond, king... City development, national war hegemony, mechanical armies, and war machines.