If you have a morning to explore Barcelona, we recommend you to take a 3h stroll seeing some of the highlights. Start at Sagrada Familia, then follow the very happening Sant Joan avenue until you reach the magnificent Arc du Triomf. Head to Parc Ciutadella and capture beautiful shots at the Gaudi fountain. Follow the path to the trendy neighborhood of Born and explore its old streets and shops - don't miss the majestic Basilica Santa Maria del Mar and we recommend you to try the cheesecake in Funky bakers (amazing) and the mouth watering pistacchio croissants in Patisserie Hofmann. Finally, cross Laietana avenue to reach the Gothic quartier where you can explore the cathedral and finish by enjoying a nice gelato at Gelaaati di Marco.
Like the Sagrada Familia, Parc Güell, is an iconic site in Barcelona with some of the most famous works of Gaudi. It is also recommended to book tickets well in advance to ensure availability. Note that the travel time to/from the Parc is quite long depending upon the location of your accommodations.
Great place for a walk in nature, at a botanical garden full of cactuses. From here you can hike up to see the view over Barcelona from the Miramar Hotel, then either take the gondola (teleferico) or continue your walk up to the castle at the top of Montjuic, also finding the funicular as another option for heading back down the mountain.