Brussels

Here's an ideal itinerary for 3 days in Brussels, taking into account your constraint of being free only at night:

Day 1:

• Evening: Start your trip with a visit to the iconic Atomium, a unique structure that offers stunning views of the city. You can also explore the exhibitions inside the Atomium, which showcase the history and culture of Brussels.

Day 2:

• Morning: Start your day with a visit to the Grand Place, the central square of Brussels that is surrounded by beautiful architecture and historic buildings. You can also visit the nearby Manneken Pis, a famous statue of a little boy peeing.
• Afternoon: Spend your afternoon exploring the Royal Museums of Fine Arts of Belgium, which houses an impressive collection of art from the 15th to the 21st century. You can also visit the nearby Magritte Museum, which is dedicated to the works of the famous Belgian surrealist artist René Magritte.
• Evening: End your day with a visit to the Delirium Café, a popular spot for beer lovers that offers over 2,000 different types of beer from around the world.

Day 3:

• Morning: Start your day with a visit to the Palace of Justice, one of the largest courthouses in the world that offers stunning views of the city. You can also visit the nearby Sablon district, which is known for its antique shops and art galleries.
• Afternoon: Spend your afternoon exploring the European Quarter, which is home to the European Union institutions and offers a glimpse into the workings of the EU. You can also visit the nearby Parc du Cinquantenaire, a beautiful park that houses several museums and monuments.
• Evening: End your trip with a visit to the Mont des Arts, a hill that offers panoramic views of the city and is home to several museums and cultural institutions. You can also visit the nearby Royal Palace of Brussels, which is open to the public during the summer months.