Top 10 Cities in Europe

1. Paris

• Eiffel Tower
• The Louvre
• Sacre Coeur
• Notre Dame
• Musée d´Orsay
• Arc de Triomphe and Champs-Elysées
• Centre Pompidou
• Seine River

2. London

• Houses of Parliament
• Buckingham Palace
• Tate Modern
• Trafalgar Square
• Tower of London
• Tower Bridge
• London Eye

3. Rome

• The Colosseum
• The Pantheon
• Palatine Hill
• St. Peter´s Basilica (Vatican)
• Trevi Fountain
• Piazza di Spagna
• Sistine Chapel

4. Berlin

Also mentioned in the post with the top 10 cities in Germany :)

5. Amsterdam

• Canal ring
• Magere Brug
• Museums: Rijksmuseum, Van Gogh Museum
• Begijnhof
• Oude Kerk and Red Light District
• Anne Frank House

6. Barcelona

• La Sagrada Familia
• Las Ramblas
• Gothic Quarter
• La Ribera: Picasso Museum
• Tibidabo

7. St. Petersburg

• Church of Our Savior on the Spilt Blood
• The Hermitage Museum
• Peter and Paul Fortress
• The Catherine Palace
• Kizhi Island

8. Vienna

• Belvedere Palace
• Hundertwasserhaus
• Schönbrunn Palace
• Prater
• St. Stephen´s Cathedral
• Albertina Museum and Gallery
• Imperial Court Theater

9. Athens

• Acropolis
• Temple of Olympian Zeus
• Theater of Dionysos
• Tower of the Winds
• Hadrian´s Arch
• Kanellopoulos Museum

10. Istanbul

• Blue Mosque
• Topkapi Palace
• Grand Bazaar
• Bosphorus Night Cruise
• Kiz Kulesi

Top 10 Cities in Germany

1. Berlin
Sights

• Brandenburger Tor
• Reichstag
• Museumsinsel: Altes Museum, Alte Nationalgalerie, Bode-Museum, Pergamonmuseum
• Fernsehturm
• Gedächtniskirche
• Potsdamer Platz and Sony Center
• Holocaust Memorial
• Gendarmenmarkt
• Checkpoint Charlie
• Bundeskanzleramt
• East Side Gallery

You can also visit Potsdam, which is just an hour away from Berlin, with amazing sights like Sanssouci Palace and Cecilienhof. You could also visit the Dutch Quarter and the Russian Colony Alexandrovka.

Munich
Sights

• Marien Square and the New Town Hall
• Cathedral of Our Blessed Lady
• Dachau Concentration Camp
• English Garden
• Hofbräuhaus
• The Victuals Market
• German Museum
• Museums Ensemble: Alte Pinakothek, Neue Pinakothek, Pinakothek der Moderne
• Olympic Stadium

Dresden
Sights

• Zwinger Palace
• Semper Opera
• Church of Our Lady
• Brühl´s Terrace
• Green Vault
• Historic Paddle Steamers
• Pfund´s Dairy
• Albertinum Museum

Weimar
Sights

• National Goethe Museum
• Schiller House
• Duchess Anna Amalia Library
• Weimar´s Old Town
• Bauhaus Museum

Also: Wartburg Castle, about 50 minutes west of Weimar

Cologne
In my opinion, Cologne doesn´t have a lot of sights, but it definitely needs to be mentioned because of the Kölner Dom.

Hamburg
Sights

• Hamburg Harbor
• St. Michael´s Church
• Speicherstadt
• Chilehaus
• Reeperbahn

Frankfurt
Sights

• The Römerberg
• The Main Tower
• Cider Taverns in Sachsenhausen
• The Senckenberg Museum of National History
• Shopping Street Zeil
• Museum of Modern Art

Heidelberg
Sights

• Heidelberg Castle
• Philosopher´s Walk
• Old Bridge´
• Old Town

Leipzig
Sights

• Bach Museum and St. Thomas Church
• Auerbachs Keller
• Monument to the Battle of the Nation
• Stasi Museum Runde Ecke

Garmisch-Partenkirchen
Amazing if you want to go skiing or hiking. You can visit the highest mountain in Germany, the Zugspitze, or hike to the amazing Partnachklamm and many other beautiful places.