This is a modernist-style building designed by Antoni Gaudí, located at number 48 Caspe Street in Barcelona. It was built between 1898 and 1900. Gaudí had the collaboration of his assistants Francisco Berenguer, Juan Rubió and Juli Batllevell, and it was the first work that Gaudí designed and built in the Eixample district of Barcelona, between party walls as rented housing.

The Casa Calvet is undoubtedly a reflection of Gaudí's artistic plenitude: it belongs to his naturalist period, a period in which the architect perfected his personal style, inspired by the organic forms of nature, for which he implemented a whole series of new structural solutions based on Gaudí's in-depth analysis of ruled geometry. To this he added great creative freedom and imaginative ornamental creation: starting from a certain baroque style, his works acquire great structural richness, with forms and volumes devoid of rationalist rigidity or any classical premises.

In 1900 he was awarded first prize in the first edition of the annual Barcelona Artistic Building Competition. In addition, the building was listed as an Asset of Cultural Interest on 24 July 1969.

Dating back to its origins, the building was built for a textile manufacturer, Hijos de Pedro Mártir Calvet, and was used both for the business, for which the ground floor and basement were used, and for housing, located on the upper floors - the owner's main floor, which was much more luxurious.

However, some experts on Gaudí's work consider the Calvet house to be the architect's most conservative work, the explanation being that Gaudí had to fit the building in with other older existing buildings and take into account the fact that it would be located in an elegant neighbourhood. Indeed, the symmetry, balance and order that characterise the Calvet house are unusual in Gaudí's work. Even so, there are modernist elements, such as the two sections of façades ending in curves on the roof, the glazed balcony overhanging the entrance and the shape of the other balconies.

In this project Gaudí resorted to a somewhat baroque style, visible in the use of Solomonic columns, the decoration with floral motifs and the roof terrace with a cascade and rococo-style flowerpots. This work marked the end of the use of historicist resources by the architect, who abandoned the use of recurring styles - such as Mudejar, Romanesque or Gothic art - which he had employed in some of his previous works, to enter a period of personal maturity and artistic plenitude in which his main inspiration would be nature, and which would culminate in works such as the Casa Batlló and the Casa Milà.

The building is located between party walls, and has five floors and a double façade, the one facing the street and the one facing the inner courtyard of the block. The building material used was ashlar stone for the exterior walls and brick for the interior; the ashlars are worked "Roman style", with a smooth frame and rough-hewn centre. The ceilings of the ground floors are supported by metal beams, while those of the flats have a Catalan vault structure, with bricks supported on iron joists, and a wooden coffered ceiling.

The façade is made of sandstone from Montjuïc, with five openings at the base, above the central one of which is the main floor tribune; above each opening is a row of balconies, in two forms, some more discreet, barely protruding from the wall, and others more prominent, three-lobed and supported on corbels, all with wrought-iron railings in the form of spirals ending in volutes. The tribune on the main floor is particularly noteworthy, decorated with the initial of the owner's surname, an olive branch (symbol of peace), a cypress (symbol of hospitality) and the coat of arms of Catalonia; it is crowned with a sculpted dome with two cornucopias of Amalthea, from which fruit is scattered, and on which two turtledoves perch. The iron railing of the tribune is decorated with mushrooms, a tribute to Mr. Calvet's love of mycology. The wrought-iron door handle, in the shape of a Greek cross striking against a drawing pin, a symbol of faith crushing sin, was forged by Joan Oñós, a blacksmith who worked regularly with Gaudí. The columns flanking the entrance are reminiscent of spools of thread, and are an allusion to Calvet's textile business.