The Tiber high valley with Città di Castello is the most important economic region in Umbria .
Economically the Tiber high valley with Città di Castello is the most important.20-25 % of Umbria 's GDP is represented by Terni steelworks ( stainless steel , titanium , alloy steel ) and the processing companies ( automotive , staninless steel tubes , industrial food facility ) .
Umbria