Frankfurt

Here's an ideal itinerary for one day in Frankfurt that meets your constraints:

Morning:

• Start your day with a hearty breakfast at Cafe Hauptwache, located in the heart of the city and just a short walk from the Hauptwache station.
• After breakfast, head to the Römerberg, the historic heart of Frankfurt. Here, you can admire the beautiful half-timbered houses and the famous Römer building, which has served as Frankfurt's city hall for over 600 years.
• From the Römerberg, take a stroll through the nearby shopping district of Zeil. Here, you'll find a wide range of shops, from high-end boutiques to department stores.

Afternoon:

• For lunch, head to Kleinmarkthalle, a bustling indoor market that offers a wide range of local and international cuisine. Try some traditional German sausages or sample some exotic fruits and spices.
• After lunch, take a short walk to the Main Tower, Frankfurt's tallest building. Take the elevator to the top for stunning views of the city and the surrounding countryside.
• If you're interested in art, head to the Städel Museum, one of Germany's most important art museums. Here, you'll find works by famous artists such as Rembrandt, Monet, and Picasso.

Evening:

• For dinner, head to Apfelwein Wagner, a traditional Frankfurt restaurant that serves local specialties such as schnitzel and, of course, apfelwein (apple wine).
• After dinner, take a stroll along the Main River, which offers beautiful views of the city skyline. If you're feeling adventurous, you can even take a boat tour of the river.
• Finally, head back to your hotel for a good night's sleep, knowing that you've experienced the best that Frankfurt has to offer in just one day!