Luther Cities

I know Rick does not include it, but I would put Worms on the list too.

Well, conceivably, you could base yourself in Berlin and reach them on day trips. A few would be around two hours each way, but it is doable, and would probably be the easiest and most convenient overall, given the plethora of trains heading out of Berlin. Smaller towns can be inconvenient to use as a central base. Einbeck would be the most difficult, and you might want to consider staying there, rather than making it a day trip.

It would be helpful to have more details; such as where you are flying into from your home, and how long you will have to travel.

If you're looking to stay in a single place I'd suggest Leipzig.

Halle (Saale)? Erfurt and Weimar too. https://www.luther-land.com/en/luther-cities

Mühlhausen was nice for a weekend.

I think it's important to consider that Leipzig and Weimar are substantial, enjoyable cities with several days of attractions aside from Martin Luther. There are some overlaps between Luther Cities and Bach Cities, BTW. It can be hard to visit more than one city by train in a single day, so a central point on a "star" rail network can be helpful.

Halle (Saale), Erfurt

I would like to follow this recommendation. It's easy to get from there to Wittenberg, Eisleben and Magdeburg by train (details at int.bahn.de). The latter takes a little longer from Erfurt, but in my view, Erfurt is the more pleasant city. There is also a fast regional train in the morning in just over 30 min. from Erfurt to Coburg, from where Luther, himself prevented from traveling through the Catholic regions, tried to influence the negotiations at the Diet of Augsburg in 1530; the train can be used with the Deutschlandticket. There is a Luther memorial museum at the impressive fortress.

If you want to go further south, you could consider Augsburg, where the Reformation in the political sense began at the Imperial Diet of 1518 and came to a provisional conclusion with the Confessio Augustana in 1530 and to a final one with the Religious Peace of Augsburg in 1555. The Carmelite monastery where Luther lived (St. Anna) is still there, as is the Fugger Palace where Luther was interrogated by Cajetan (unfortunately not open to the public as it is still the seat of the Fugger administration).

there are some overlaps between Luther Cities and Bach Cities, BTW.

And two of them in easy reach from Halle or Erfurt would be (1) Arnstadt (Bach's first organist position 1703-1707; since 2000 the reconstruction of the Wender organ, which was Bach's instrument, has stood there), and (2) Köthen, where Bach married his second wife Anna Maria, whose name is associated with the “Clavierbüchlein”.

And if you like to add a bit of modern architectural history and parkland, the Bauhaus in Dessau and the Wörlitz Gartenreich are not far away either.

Good that you include Magdeburg as an historically Luther connected city, all the more so in light of the utterly horrific event wreaked upon the city in the Thirty Years War.

In July of 2009 I spent two full days exploring Magdeburg, another city you can walk across the Elbe bridge. At that time the Magdeburger Dom (the sign there states that Luther had preached there and its consequence) was undergoing refurbishing, refitting, and so.