Heilbronn sits on the Neckar in northern Baden-Württemberg, surrounded by vineyards and rebuilt city streets. It was heavily bombed in 1944, so you do not come here for a perfectly preserved old town. You come for the pieces that survived or were rebuilt with care, and for a city that still knows it is a wine town.
The centre is compact. Kilian's Church gives Heilbronn its strongest historic anchor, while the town hall's astronomical clock adds a fine Renaissance flourish to the market square. Along the Neckar, experimenta is one of Germany's largest science centres and makes the city much more than a quick lunch stop.
The best finish is up on the Wartberg or along a vineyard path, looking back over the river and red roofs. Heilbronn is not as obvious a day trip as Heidelberg or Stuttgart, but it has enough of its own shape to reward a spare day nearby.