Barcelona is a vibrant and diverse city located on the northeastern coast of Spain, offering a rich cultural heritage and an abundance of activities and sights for visitors of all ages. Here is a detailed overview of some popular things to do and see in Barcelona:

1. Park Guell: Park Guell is a public park located on Carmel Hill that was designed by Antoni Gaudi and is considered one of his most famous works. The park features a combination of nature, architecture, and art, with a number of whimsical mosaics, sculptures, and viewpoints. Some of the most famous attractions include the mosaiced terraces, the lizard statue, and the tiled bench that offers panoramic views of the city.
2. La Sagrada Familia: La Sagrada Familia is a massive cathedral that has become one of the symbols of Barcelona. The cathedral was designed by Antoni Gaudi and is a fusion of Gothic and Art Nouveau styles. Visitors can take tours of the interior, including the Nativity façade, the Passion façade, and the crypt, as well as climb to the top of one of the towers for panoramic views of the city.
3. Casa Batllo: Casa Batllo is another stunning example of Gaudi’s work, and is considered one of the most beautiful buildings in Barcelona. The building was originally a private residence, but is now a museum showcasing the architect’s unique style and vision. Visitors can explore the interior, including the impressive central courtyard, the tiled roofs, and the stained glass windows, as well as learn about the history of the building and its restoration.
4. Gothic Quarter: The Gothic Quarter is a historic neighborhood located in the center of Barcelona that is filled with narrow streets, squares, and medieval buildings. The quarter is also home to a number of trendy shops, restaurants, and cafes, as well as some of the city’s most famous landmarks, such as the Cathedral of Santa Eulalia, the Plaça del Rei, and the Picasso Museum.
5. Picasso Museum: The Picasso Museum is dedicated to the works of Pablo Picasso, one of the most famous artists of the 20th century. The museum houses one of the largest collections of his works, including early pieces from his Blue and Rose periods, as well as more mature works. Visitors can explore the galleries, as well as attend special exhibitions, educational programs, and guided tours.
6. La Rambla: La Rambla is a busy boulevard located in the heart of Barcelona that is lined with street performers, flower stalls, and cafes. The boulevard is a popular destination for shopping, dining, and people-watching, and is also home to some of the city’s most famous attractions, such as the Liceu Theatre, the Gran Teatre del Liceu, and the Columbus Monument.
7. La Boqueria Market: La Boqueria Market is a famous indoor market located near La Rambla that is a feast for the senses. The market is home to a number of stalls selling everything from fresh produce and exotic spices to seafood, meats, and sweets. Visitors can browse the stalls, sample the food, and learn about the local cuisine.
8. Montjuic Castle: Montjuic Castle is a hilltop fortress located on Montjuic Hill that offers stunning views of the city and the sea. The castle was originally used as a military prison, but is now a museum showcasing its history and its role in the Spanish Civil War. Visitors can explore the grounds, including the exhibitions, the terraces, and the gardens, as well as attend special events and activities.
9. Barceloneta Beach: This bustling beach is a popular spot for sunbathing, swimming, and playing beach sports, and is also home to a number of seafood restaurants and beach bars.
10. Magic Fountain: This impressive fountain is a popular evening attraction, offering a light and water show set to music.
11. Camp Nou: This iconic stadium is home to FC Barcelona, one of the world’s most famous football clubs, and offers tours of the grounds and museum.
12. Casa Mila: Another stunning example of Gaudi’s work, this former private residence is now a museum showcasing the architect’s unique style and vision.

There are many other sights and activities to enjoy in Barcelona with teens, including theaters, museums, shopping centers, and theme parks. Regardless of your interests, Barcelona offers something for everyone, making it an ideal destination for families with teenagers.