Ostrava
Ostrava is a big old industrial city with grey buildings and heavy industrial. If you want to see "socialism realism" visit some of the Ostravas
sub urbans. Coal mining and steel production has always been main income sector of Ostrava and therefore you find a lot of remnants.
Because a coal mining Ostrava was previously guite polluted. Although mining within the city limits was stopped in 1994 a lot of factories are still left. At the tourist info in the town hall you can get information what to visit, if you are interested in industrial sights and huge factory installations.