The Berlin Marathon runs through the Brandenburg Gate in late September. The gate itself - the 18th-century neoclassical arch that divided the city for 28 years and is now the most photographed finish line in marathon running - is eight kilometres from Sanssouci Park in Potsdam, and 250 kilometres from the Baltic coast at Rostock. Both are on the same rail corridor. This itinerary makes the most of Germany's Intercity network to take you from the palace gardens of the Prussian kings to the salt air of the north German coast in four days of progressively lower effort.
Nights One and Two: Potsdam
The S7 S-Bahn line runs directly from Berlin Hauptbahnhof to Potsdam Hauptbahnhof in 25 minutes, every ten minutes throughout the day. Either puts you in Potsdam before the morning is properly underway.
Potsdam is the former seat of the Prussian kings - a city of palaces, gardens, and lakes constructed over three centuries. The centrepiece is Sanssouci Park, 290 hectares of landscape gardens stretching west from the city, containing eight palaces and numerous smaller architectural follies connected by flat gravel and tarmac paths. It is, for the purposes of this trip, one of the better pieces of luck available to anyone who has just run a marathon: the paths are wide, level, and designed for contemplative walking at pace.
The main palace, Sanssouci itself, was built by Frederick the Great between 1745 and 1747 as a summer retreat. Sanssouci means "without worries" in French, which was the court language of the Prussian aristocracy. The Neues Palais at the western end of the park has the better interiors; the Orangerie Palace in the centre of the park has the best views. Entry to individual palaces costs €8 to 14; a combination ticket covers all open buildings for around €25. Buy tickets online in advance.
The Dutch Quarter (Hollandisches Viertel) in central Potsdam - 134 red-brick gabled houses built in the 1730s - is worth an afternoon. The streets are flat and the cafes and boutiques are a 15-minute walk from Sanssouci's eastern entrance.
Where to eat: Restaurant Juliette on Jagerstrasse in the Dutch Quarter serves French cuisine with Brandenburg produce - one of the better kitchens in Potsdam.
Nights Three and Four: Rostock and Warnemunde
On Wednesday morning, take the Intercity train from Potsdam Hauptbahnhof north to Rostock. The journey runs 2 hours, passing through Schwerin and the Mecklenburg lake district.
Rostock is the largest city on Germany's Baltic coast - a Hanseatic trading port whose medieval commercial architecture along the Kropeliner Strasse and the Neuer Markt survived the Second World War better than most north German cities. The Marienkirche (St Mary's Church), a 13th-century brick Gothic cathedral, contains an astronomical clock from 1472 that still functions and is one of the oldest of its kind in Europe.
The S-Bahn line S1 connects Rostock Hauptbahnhof to the coastal suburb of Warnemunde in 22 minutes. Warnemunde is the reason to be in this part of the Baltic coast: a fishing village retaining its own distinct character, with the lighthouse at the harbour mouth, the canal-side houses painted in the faded pastels of north German coastal tradition, and - most relevant - a flat, tarmac promenade running the full length of a wide sand beach.
The Warnemunde Promenade runs for approximately 3 kilometres along the Baltic beachfront. In late September the sea temperature sits around 14 to 16°C - cold enough to clear your head. The beach is wide, firm sand and requires nothing of your legs whatsoever.
Where to eat in Warnemunde: Restaurant Kogge on the Alter Strom serves Baltic fish - smoked eel, herring, pike-perch - in a setting that has the correctly weathered quality of a north German harbour restaurant.
Getting Home
Direct Intercity trains from Rostock Hauptbahnhof to Berlin Brandenburg Airport (BER) run in approximately 2 hours. The service calls at Berlin Sudkreuz, which has a direct shuttle bus to the airport terminal. This bypasses central Berlin entirely - you go from the Baltic coast to your departure gate without returning to the city at all.