Frankfurt

Comfortably one district, because the train takes twelve minutes.

1. 1Deutsche Bahn gives the S8 or S9 from the regional station under Terminal 1 to Frankfurt Hauptbahnhof as about 12 minutes, on average every 10 minutes, from platforms 103 and 104.
2. 2There are two stations and mixing them up costs you the connection. The regional one is on Level 0 of Terminal 1; the long-distance station is separate, about five minutes' walk away.
3. 3A taxi is 20 to 30 minutes depending on traffic and runs around the clock at both terminals, which is what covers you outside the S-Bahn's hours.

Both banks of the Main, which here is a walk rather than a journey.

1. 1The Altstadt, the Zeil and the Kleinmarkthalle are one side. Alt-Sachsenhausen and the apple-wine taverns are directly across the river.
2. 2The Kleinmarkthalle is closed on Sundays and public holidays and shuts at 16:00 on Saturdays, which is the thing most likely to break a market plan.
3. 3After a Gulf rotation the constraints here are different in kind rather than degree, with one exception: drugs are treated severely and the FCDO is explicit that this covers transiting the airport.

The city twice over, with an afternoon still spare.

1. 1The centre is small enough that a full day is the Altstadt, the Zeil and Sachsenhausen with time left for the Westend or the museum bank.
2. 2July and August are actually the wettest months, at 63.5 and 61.4 mm, and April the driest. There is no dry season here, so a rain layer travels regardless of the month.
3. 3About 64 frost days a year fall between November and March, which makes icy mornings normal rather than notable in that window.