Köln

Here's an ideal itinerary for 3 days in Köln that meets all your constraints:

Day 1:

• Morning: Start your day with a hearty breakfast at Café Fassbender, known for its delicious pastries and coffee.
• Afternoon: Head to the Rheinpark, a beautiful park located on the banks of the Rhine River. You can rent bikes or take a stroll along the river, enjoying the scenic views.
• Evening: For dinner, head to Hanse Stube, a Michelin-starred restaurant that serves exquisite German cuisine. After dinner, head to the famous Alter Markt square, where you'll find plenty of bars and pubs to party the night away.

Day 2:

• Morning: Start your day with a visit to the Kölner Dom, one of the most iconic landmarks in Köln. This stunning cathedral is a UNESCO World Heritage Site and is definitely worth a visit.
• Afternoon: For lunch, head to Brauhaus Früh am Dom, a traditional brewery that serves delicious local beer and hearty German food.
• Evening: For a night out, head to the trendy Belgian Quarter, where you'll find plenty of bars and clubs to choose from. Try out the cocktails at Shepheard Cocktailbar or dance the night away at Club Bahnhof Ehrenfeld.

Day 3:

• Morning: Start your day with a relaxing spa session at Claudius Therme, a luxurious thermal bath complex that offers a range of treatments and facilities.
• Afternoon: For lunch, head to Die Fette Kuh, a popular burger joint that serves some of the best burgers in town.
• Evening: For a fancy dinner, head to Le Moissonnier, a Michelin-starred French restaurant that offers a unique dining experience. After dinner, head to the chic rooftop bar of the Hotel im Wasserturm for some drinks and stunning views of the city.

I hope this itinerary helps you plan your trip to Köln and enjoy all the amazing things this city has to offer!