Key Points:
Barcelona is one of the best travel destinations and one of the top cities to visit in the world.
Nomadic Matt has provided a pretty good travel guide for Barcelona.
The primary things to do in Barcelona include: the Barri Gotic and Barcelona Museum of Contemporary Art (MACBA) (1 day), GaudÃ’s architecture (1 day), the Picasso Museum and Montjuïc Hill (1 day), Girona (1 day).
According to Wikipedia, "Barcelona is a city on the coast of northeastern Spain. It is the capital and largest city of the autonomous community of Catalonia, as well as the second most populous municipality of Spain. It is one of the largest metropolises on the Mediterranean Sea, located on the coast between the mouths of the rivers Llobregat and Besòs, and bounded to the west by the Serra de Collserola mountain range, the tallest peak of which is 512 metres (1,680 feet) high."
Here we quote the best way to travel in Barcelona provided by Nomadic Matt, a New York Times best-selling author of How to Travel the World on $50 a Day and Ten Years a Nomad, as well as the founder of his website.
Check ChatGPT's answer for alternative itinerary.