Building between partitions, renovated and extended on several occasions. It retains an interesting social lounge and an eclectic performance hall. The value of this building is that of citizen representativeness. The only interesting element on the façade is the curved balcony on the first floor, with interesting wrought iron work. It has three low arched openings and two side balconies. The Casino is located in the 19th century area that was built up after the demolition of the old medieval wall and was initially occupied by rental flats. It later became an area of leisure, commercial and social activities. The Casino Unió Comercial is an entity born from the merger, in 1918, of the old Centre or Casino de la Unió (1853) and the Industrial and Commercial League. In 1922, the balcony and the arches of the first floor were built in accordance with the refurbishment project of A. Pons i Domínguez, preserved in the municipal archive of Vilafranca.

It is a building between partitions with a rear courtyard and with façades to the square and the passage. It is a single-family house in its origins, later adapted to social uses. The property has a rectangular plan and consists of a semi-basement, a mezzanine, two floors and an attic. The roof is partly gabled and partly flat. It consists of four corridors perpendicular to the façade separated by a load-bearing wall. The main staircase has four sections and is attached to the partition. In the hall we find two lowered arches and a central column. There is a covered back gallery that forms the front facing the courtyard. The load-bearing walls are of common masonry and brick. The forge is made of wooden beams and tile surround. In the semi-basement there are lowered tile vaults. The roof is made of Arabic tiles with a structure of wooden beams and slats and tiles. The staircase is covered by Catalan vaults. The main façade is symmetrical and is composed of four vertical axes that correspond to the four corners. The ground floor has four low arched portals. The first floor has two balconies running from two openings with a lintel each, crowned with drip edges. On the second floor there are four balconies of an opening crowned with a cornice. The top of the building is composed of a cornice and flat baluster railing. The rear façade is composed according to six vertical axes with lowered arched openings on the semi-basement and mezzanine floors and with galleries with lintels on the upper floors.

L'edifici del Mercantil pertany a un estil eclèctic. La façana la podem dividir en cinc parts: en la central, més avançada, és on trobem l'entrada principal; en la part alta hi ha el nom de l'entitat i en el centre l'any de la seva fundació; una galeria coberta uneix els dos cossos extrems amb el central. Els elements decoratius són els esgrafiats, col·locats en els timpans de les dues obertures que flanquegen l'edifici, i la ceràmica de reflexes metàl·lics a mode de fris. De l'interior cal destacar el teatre; entrant trobem l'amfiteatre de platea, després la platea voltada lateralment per llotges. Els primer pis té una zona central amb butaques i dues de laterals amb grades. Tot voltat per un jardí molt ben cuidat. El "Centro Mercantil, Industrial y Agrícola" havia estat fundat l'any 1899 com a conseqüència d'una desavinença entre diversos membres de l'antic "Casino de Recreo", uns, partidaris dels "Godó" i els altres, dels "Boyer". El local social de l'entitat va ésser edificat en el solar on antigament hi havia hagut el teatre Tívoli, i la seva inauguració coincidí amb el dia de la Festa Major de l'any 1899. El Cercle Mercantil celebrà el seu cinquantenari l'any 1949. Conté un teatre, un saló-café, una sala de festes i un jardí. Construït seguint un projecte de l'arquitecte Francesc de B. Galtés; dirigides les obres per Francesc Sellés; la decoració a càrrec de Frederic Brunet i la pintura pe Bartomeu Camps i Antoni Tomàs.

Civil building. Its interest lies in the adaptation of a new building to the old country house, located in the centre of the complex, of which the ground floor, the access door and one of the Gothic windows on the façade are preserved. The new building covers the defense tower and reproduces the original windows. The left side of the Casino constitutes the theatre area and the right side is made up of the main entrance and the Rotunda, on the roof of which the intersections of the framework are finished with decorative elements so that they look like hanging keys. The architectural elements are absolutely heterogeneous: Gothic, neoclassical, modernist and eclectic. Theater It has a neoclassical and romantic nature. It consists of a platform with lateral tribunes on the ground floor and a roughly semicircular curved balcony supported by cast iron columns. The decorations, mouldings and ceiling panels are made of plaster. The wrought iron railings and modernist lamps are also interesting. Some pieces of this theatre are reused from some places of Barcelona. Forgings The old Mas Vell Casino gate closes the garden. The access door is in the centre and on it are the initials M.A. of its former owner, Miquel Amat. It is made of iron and consists of a set of parallel and crossed bars. There are rows with vegetal elements and sinuous lines, typical of modernism. Constructive elements that demonstrate the marked modernist trend of the Casino. They observe how both the door handle or the wrought iron of the rotunda's pergola accentuate the decorative value through sinuous, asymmetrical curves that end in squiggles or spirals. The "Casino" del Masnou was born as an entity in 1876. The idea of a new building was put into practice by Pere Grau Maristany -Count of Lavern-, located in the "Can Fontanills" country house, owned by Miquel Amat i Lluch. In 1903, the Rotunda, game rooms, billiards and other outbuildings were inaugurated. In 1904, the theatre also opened. The modernist main entrance is from 1902.

Detached single-nave building with foyer, hall with amphitheatre and stage. The structure is made of load-bearing walls with wooden trusses and metal beams. The main façade is symmetrical and consists of three sections separated by ornamental pilasters. The axis of symmetry is emphasised by the segmental-arched entrance door, the marquee and the pointed-arched window that links with the ornamental motifs of the pediment. The roof is gabled. The interior has been renovated. The hall has plaster pilasters, capitals and false diaphragm arches. The frame of the stage is decorated with garlands, vegetal and floral elements with a large mask in the centre.

A small building (approximately 5 x 5 metres) with an octagonal floor plan. The eight walls are identical: they have a large window framed in stone with simple mouldings and closed with shutters, with a small spiral made of tiles on top. Each wall ends in a skewer, transforming into a gable roof (there are eight roofs in total) that meet in the centre, where a six-sided pyramidal roof starts. The set of roofs is the most interesting part of the building. The roof is topped by an iron weather vane with figures on it. The wall facing north-west is the one with the entrance door, and at the top there is an iron cross. On the roof, the pyramid's ridges are made of blue glazed ceramic. It is a gazebo or private viewpoint – a suitable place to go and enjoy the view (from here you can see the whole village, the Pyrenees...). It was built at the beginning of the 20th century by the Vilaclara family (originally from the Vilaclara de Sant Feliu country house), after they had settled in the village.

Three-storey rectangular building between partitions made up of three vertical sections: two at the sides (multi-purpose hall and theatre) and a central section (stairwell) that separates and distributes. The roof of the halls is gabled with the ridge perpendicular to the main façade. The roof of the stairwell, on the other hand, is flat with a terrace. The facing, made of plastered and painted brick, is of well-squared ashlars with a bush-hammered plinth in the central section and smooth in the side sections. The crown of the building is characterised by a structure of two pediments flanking the quadrangular section of the staircase. The pediments are almost identical and have smooth, undecorated tympana. One of them has a balcony decorated with corbel-shaped corbels, arranged on a frieze that runs along the entire façade, ornamented with rectangular elements that imitate pilasters and are crowned by spheres. As for the openings, they are distributed symmetrically on the ground floor and first floor, with the exception of the balcony described above, which would be independent and the only opening on the second floor. The entrance door is on the ground floor, flanked by eight symmetrically distributed openings consisting of two segmental arch doors and two lintelled windows. The first floor has a central balcony with a basket-handle arch and a projecting balustrade, which is flanked by three balcony windows. Its characteristic, and what gives the building its value, is the use of elements of classical design such as pilasters with Ionic capitals and semicircular arches decorated with plant motifs. This building was inaugurated in 1922, and throughout its history it has undergone several phases of restoration. Promoted by the Borràs industrial family, who had a factory in the municipality, it became one of the most important cultural centres in Castellbell i el Vilar. Since 1991, it has been owned by the town council. In December 2001 serious structural problems were detected that forced the closure of its activity and even the temporary eviction of a savings bank located on the ground floor of the building. At that time, significant cracks were detected in one of the walls and the ceiling had caved in. When its structure was analysed, it was found that one of the central beams in the room had collapsed by about 15 centimetres. Almost a year and a half later (in 2003) the first works began: renovation of the roof and replacement of the trusses - which were all wooden and were found to be badly damaged - with metal ones. In addition, the walls most at risk were tied down and the opportunity was taken to carry out an initial remodelling of the hall. With this intervention, the theatre was able to reopen. In 2008, work began on renovating the stage machinery - electrically operated curtain rails, renovation of the entire electrical installation, lighting, curtains... - and the wooden stage was replaced with new, fireproof flooring. Finally, all the stairs to the stage were renovated, the doors and accesses were readapted and the dressing rooms and exterior façade were redone.