Describing Karviná as a spa town is really a little misleading. Although there is a spa in the nearby Darkov, Karviná looks very different from your typical image of a clean, tranquil spa town. In fact, it is one of the centres of the (now declining) coal mining industry. There is a pretty town square, a little chateau and an animal park you can visit. The rest is all communist-built shopping centres and not so attractive hypermarkets that have sprung up in the 90s.
You can get in by bus from nearby towns like Ostrava, Český Těšín, Havířov or Orlová (at least once an hour).
You can also get in Karviná by train. There is a direct connection to Prague,Žilina or Košice. The biggest railway junction in the area is Bohumín, which is connected to the most surrounding railway lines in Czech republic and also to railway line to Poland.
Going by bus is cheapest way to travel around Karviná. One bus ticket is about CZK 15 (approx. 0.6 €).
You can as well go by taxi, about CZK 20 per km (approx. 0.7 €)