At the beginning of the century, Gaudí was working on numerous projects simultaneously. They reflected his shift to a more personal style inspired by nature. In 1900, he received an award for the best building of the year from the Barcelona City Council for his Casa Calvet. During the first decade of the century Gaudí dedicated himself to projects like the Casa Figueras (Figueras house, better known as Bellesguard), the Park Güell, an unsuccessful urbanisation project, and the restoration of the Cathedral of Palma de Mallorca, for which he visited Majorca several times. Between 1904 and 1910 he constructed the Casa Batlló (Batlló house) and the Casa Milà (Milá house), two of his most emblematic works.
Commissioned by the company Hijos de Pedro Mártir Calvet, Gaudí built the Casa Calvet (1898–1899), in Barcelona's Carrer Casp. The facade is built of Montjuïc stone, adorned with wrought iron balconies and topped with two pediments with wrought iron crosses. Another notable feature of the facade is the gallery on the main floor, decorated with plant and mythological motifs. For this project, Gaudí used a Baroque style, visible in the use of Solomonic columns, decoration with floral themes and the design of the terraced roof . In 1900, he won the award for the best building of the year from Barcelona City Council.
A virtually unknown work by Gaudí is the Casa Clapés (1899–1900), at 125 Carrer Escorial, commissioned by the painter Aleix Clapés, who collaborated on occasion with Gaudí, such as in decorating the Palau Güell and the Casa Milà. It has a ground floor and three apartments, with stuccoed walls and cast-iron balconies. Due to its lack of decoration or original structural solutions its authorship was unknown until 1976, when the architect's signed plans by Gaudí were discovered. In 1900, he renovated the house of Dr. Pere Santaló, at 32 Carrer Nou de la Rambla, a work of equally low importance. Santaló was a friend of Gaudí's, whom he accompanied during his stay in Puigcerdà in 1911.It was he who recommended him to do manual work for his rheumatism.
Also in 1900, he designed two banners: for the Orfeó Feliuà (of Sant Feliu de Codines), made of brass, leather, cork and silk, with ornamental motifs based on the martyrdom of San Félix (a millstone), music (a staff and clef) and the inscription "Orfeó Feliuà"; and Our Lady of Mercy of Reus, for the pilgrimage of the Reus residents of Barcelona, with an image of Isabel Besora, the shepherdess to whom the Virgin appeared in 1592, work of Aleix Clapés and, on the back, a rose and the Catalan flag. In the same year, for the shrine of Our Lady of Mercy in Reus, Gaudí outlined a project for the renovation of the church's main facade, which ultimately was not undertaken, as the board considered it too expensive. Gaudí took this rejection quite badly, leaving some bitterness towards Reus, possibly the source of his subsequent claim that Riudoms was his place of birth. Between 1900 and 1902 Gaudí worked on the Casa Miralles, commissioned by the industrialist Hermenegild Miralles i Anglès; Gaudí designed only the wall near the gateway, of undulating masonry, with an iron gate topped with the four-armed cross. Subsequently, the house for Señor Miralles was designed by Domènec Sugrañes, associate architect of Gaudí.