The Arc de Triomf was built in 1888 as the main entrance to the Exposición Universal de Barcelona. It was designed by the Catalan architect Josep Vilaseca i Casanovas and features sculptures by Josep Reynés, Josep Llimona and Manel Fuxa.
The 30 metre high mudejar style brick arch is the focal point at the end of Passeig de Luis Companys. I suggest you combine it with a visit to the nearby Parc de la Ciutadella.
Where Passeig de Luis Companys joins Passeig de Sant Joan
How to get there:
The nearest metro stop is Arc de Triomf on the red line (L1)