Besides
Poland, the
Czech Republic contains a portion of historical Silesia.
AFAIK Germany does too.
The largest city in the Czech portion of Silesia is
Ostrava, traditionally linked to
heavy industry; the city is highly
polluted and has problems with
mines leading under the city itself, causing, for example,
ground sinkage problems.
One easy place to find a mildly distorted featureless
map of Silesia is the map for the
game Diplomacy.