**2.4. Plaça del Rei**

**2.1. Plaça Sant Felip Neri**

46 From Natural to Artificial Intelligence - Algorithms and Applications

**2.2. Carrer del Bisbe-Carrer de Santa Llúcia**

**2.3. Plaça de Sant Iu**

This quiet and secluded public square, located at the end of Montjuïc del Bisbe street, is one of a set of closed squares in the Ciutat Vella of Barcelona. Its floor plan shows an irregular pentagon boundary figure with a central fountain. The 505 sqm plan presents a uniform stone floor material and is completed by five façades made of stone material as well. Of the five façades, one is Sant Felip Neri church, while the others house a school, a hotel, some dwellings and the parish stances. Three big, old trees with an asymmetric distribution in plan cover the square with their foliage. Their trunks serve as irregular columns that support the green ceiling, enclosing the square and preventing people from seeing the open sky. No sound of traffic is heard, because the Plaça is far from main roads. However, the noise of shouting children fills the square every morning, when a group play during breaktime in their beautiful schoolyard: Plaça Sant Felip Neri. During the rest of the day, a few groups of tourists arrive and look to the pockmarked stones on the church façade; marks that remind us of the Spanish Civil War. At any time of day, a street musician may use the square to play the guitar or violin in the most distant corner or near the central fountain, accompanying with music couples who are out walking, in a romantic scene.

This little crossroads near the cathedral square seems an ordinary place. Nevertheless, a closer examination reveals that some factors come together in this single crossing. Geometrically, the floorplan forms a T pattern in which the crossing point coincides with the bishop's palace door. This door, when opened, reveals an interior courtyard that enlarges Carrer de Santa Llúcia, leading into this peaceful enclosure. The façade of Santa Llúcia chapel in the same corner gives a monumental and ceremonial character to the place. On the opposite side, the entrance to the Casa de La Ardiaca museum is prolonged by a ramp. During the day, some street vendors invade the corner and try to sell their products in front of Santa Llúcia chapel or at the beginning of the ramp. However, the Bishop's palace door is always fully clear, because of the presence of a guard when the door is open, or even on account of the large number of people who circulate through Carrer del Bisbe. Only at night, and particularly on Saturday nights, people tend to fill the area in front of the closed door of the bishop's palace standing up and looking in the opposite direction. There, an old man sings opera arias and recitatives over an amplified orchestral base. His voice invades the corner and goes beyond those limits, turning the old streets into an urban opera theatre.

Like a widening of the street, Plaça de Sant Iu is located in front of the eastern door of the cathedral. A gigantic gothic door crowned by an octagonal bell tower constitutes the west façade of this little square. On the opposite façade, a gallery formed by five stone arches closes the square. The north façade is formed by the classic-style entrance of Frederic Marès museum, whilst the south façade presents a flat wall without any door that serves as a perfect backstage for street musicians. This is the preferred point for buskers in Plaça de Sant Iu, not only because of the presence of the big wall behind them, but also because of a long stone bench on the east façade that allows listeners to sit down. In this privileged environment, groups of one, two or three musicians sing or play their instruments. A unique stone material

covers the four façades of the square and the floor and gives it a uniform appearance.

Some meters behind Plaça de Sant Iu is Plaça del Rei, a totally different environment both in size and proportions. There are no trees in this 745 sqm area of stone pavement, whilst its four façades enclose the square up to a height of 20 m. In the north corner of the square, a monumental staircase rises from the floor to the Museu de la Ciutat door. Usually, street musicians enliven the atmosphere with their instruments every day, and crowds of tourists occupy the entire square looking at the real shields on the walls, the pointed arches of the windows, or the tower of Santa Àgata chapel. The everyday life of the square is always very busy, and total silence only occurs when the square transforms into a concert hall for choir, orchestra or band performances. At these times, the players are usually situated on the corner stairs and the public occupy the rest of the square. When this happens, the sound of the musicians can be heard bouncing on the hard stone of the rear walls creating a sense of spatiality that envelopes the audience.
