Beautiful iron Dom Luis I bridge over Douro river in Porto, Portugal, Europe

arch bridges arch bridge beautiful bridges bridge city center city centre constructions construction cultural monuments cultural monument cultural sites cultural site deserted douro river douro downtown duero empty europe famous place gustave eiffel heritages heritage historical historic center historic centre historic city center historic city centre historic old town historic inner city inner town iron midtown nobody no one no people northern portugal old towns old town place of interest ponte dom luis i bridge ponte dom luis i ponte dom luis i portugal portuguese rio douro river rio douro rivers river sights sight southern europe south europe steel buildings steel building tourist attractions tourist attraction town center town centre travel photography travel unesco world heritage sites unesco world heritage site unesco world heritage uninhabited world heritage site