The other side shows Trieste (or Triest in German) which, until 1918, was the most important Austrian maritime port. After WW1, the Austrian-Hungarian monarchy came to an end, and Trieste became part of Italy. The scenery and also the old coat of arms refer to the pre-WW1 city.

A larger and more detailed image is here:
http://www.numismatico.de/files/at-20euro_257.jpg
The coin is available in proof only and can thus not be purchased at face value. The EU price is about €35; mintage is 50,000. This is the fifth coin in a series of six:
2004: SMS Novara, SMS Erzherzog Ferdinand Max
2005: Admiral Tegetthoff (Polar Sea Expedition), SMS Sankt Georg (that one also features the Statue of Liberty)
2006: SMS Kaiser Franz Joseph (Merchant Navy), SMS Viribus Unitis (Navy)
That last coin in the Maritime History series will come in September/October.
Christian