The main attraction is the medieval Altstadt old city located on an island surrounded by the Trave river and channels. Listed as an UNESCO heritage site (http://whc.unesco.org/en/...), it offers an astonishing variety of different architectural styles. The streets of Lübeck are a delight for a connoisseur of architecture.
Bear in mind that Lübeck's Altstadt is not an open-air museum but a living city centre, so don't expect a complete medieval site. You'll find many beautiful old buildings intertwined with modern ones and a modern infrastructure. A particularly well-preserved 13th c. part of the Altstadt is the Koberg area at the island's northern end. And don't miss the Gänge, small streets off the bigger roads, with small houses and a peculiar atmosphere.
Noteworthy historical buildings include:
The churches, housing several of the finest Northern German artworks: St. Marien or Marienkirche: the biggest one, a fine brick gothic building, located near the Rathaus city hall at the very centre of the Altstadt; the Dom: very nicely situated on the quiet southern end of the island, contains a wooden crucifix by Bernd Notke; St. Petri or Petrikirche, near Marienkirche: its tower platform to be reached by an elevator offers a great view over the city, and if weather conditions allow it you can even see Travemünde 17 km to the north-east; St. Jakobi or Jakobikirche: north of St. Marien, at the Koberg; St. Aegidien or Aegidienkirche: the smallest one, in the eastern Altstadt; St. Katharinen or Katharinenkirche without a tower: south of St. Jakobi, contains works of Ernst Barlach;
The two remaining city gates: Holstentor near train station/ZOB bus terminal and Burgtor northern Altstadt; they both contain museums nowadays; Buildings in Lübeck
Heiligen-Geist-Hospital near Koberg;
Classicist Behnhaus/Drägerhaus in KönigstraÃe, hosting an art museum;
The Rathaus or city hall: its architecture is a stylistic potpourri reaching back to the 12th c. Note that it is still the seat of the city administration and not a museum, so you're not expected to have a look inside on your own. But there are guided tours every hour or so where the many historic rooms and the gallery of city leaders' portraits are explained in German and possibly other languages.
The Willy Brandt House: His childhood home has now been turned into a museum about his life and career in politics. Entrance is free.
There are two houses dedicated to Lübeck's two literature nobel prize laureates: The Buddenbrookhaus is dedicated to the brothers Thomas and Heinrich Mann, who spent their youth there, and contains many of their works. It's near Marienkirche, in MengstraÃe. Then there is the Günter-Grass-Haus of The Tin Drum fame in GlockengieÃerstraÃe.
The Museumshafen museal port between Beckergrube and the Musik- und KongreÃhalle building features some old-fashioned ships, among them a rebuilt Hanseatic kraweel "Lisa von Lübeck"âmore so in winter, because many of these ships are still in use during summer.
The borough of Moisling has a special Jewish history. An old Jewish cemetery is still to be found there.