North Frisian Islands
Be advised that this is largely a rural area with tourism as its main (and sometimes only) economic activity of note, so the term "city" is a stretch even for the one(s) listed here
- Westerland on Sylt
- The Halligen, small islands and islets that are almost completely submerged during high floods save some Warften (artificial hills with most of the settlements on them). The biggest and most well known of them is Hallig Hooge (pronounced with a long "o").
These islands are geologically different from the East Frisian islands in that they don't mostly consist of sand and dunes, but are rather remnants of former mainland that were cut of by the rising sea as well as storm floods and human mismanagement. The whole area is influenced by the constant struggle of its inhabitants against nature, gaining, losing and reclaiming land since probably Roman times.
The North Frisian Islands are located in Germany so all locals speak standard German. The region is officially bi-lingual and actually tri-lingual as not only is the Frisian language still taught and spoken, Danish, Low German and South Jutlandic ("Low Danish") plays a local role as well. both are protected by law. Frisian is interesting in that is the closest relative to modern English still spoken.
Westerland on Sylt has an airport with some seasonal connections to Southern German destinations. However, unless you are headed to Sylt first and foremost, its location in the Northwestern "corner" of this area makes it an awkward access point, despite its railway connection to the mainland. Besides that a number of islands, for example Föhr and Heligoland have small airfields for private aircraft. For private charter Air Hamburg is one possibility. Hamburg (IATA: HAM) airport is the closest with major airline connections. That being said, unless you are already in (Northern) Germany, you will most likely find arriving by air cumbersome and too expensive for hardly any value added.
Most islands are connected by boat to several points on the German mainland. Heligoland is among the best connected with a number of boats leaving almost every day from some ports in the summer high season.
Westerland on Sylt is connected to the mainland via the railway-only Hindenburgdamm (named for the infamous Reichspräsident, several attempts at changing the name after 1945 have failed) and trains are avialable from many points in Germany, there is even limited Intercity and ICE service. The Sylt Shuttle also transports cars.
Depending on the size of the islands you can either walk, cycle or even drive a car (mainly on Sylt). Keep in mind that while the terrain is flat it can get windy, making cycling against the wind a daunting task to some.
- Bird watching
Bear in mind that even in cold and windy weather you can get severely sunburnt. To avoid the immediate unpleasantness and a potential of a higher risk of skin cancer cover as much skin as possible and apply sunscreen (widely available, Sonnencreme or Sonnenmilch in German) to exposed areas even if the temperature is "only" 25°C