Art Nouveau and eclecticism arrived together with the mining boom in the city of La Unión. The industry led to the flowering of a new form of construction that was associated with new ideas at the time. It was a city that needed to be built, winning its freedom from Cartagena in 1860 and with some rising population figures. Mining businessmen, predominantly mine owners, had amassed vast amounts of money and aimed to leave their mark in one way or another. They achieved this through architecture, either by building their own residences in towns or suburbs or other public or private buildings.

In the last quarter of the 19th century, the wealthy bourgeoisie in La Unión constructed buildings in line with the Art Nouveau of the era, characterised by features that made this new style a rejuvenating trend. These buildings were made of steel, glass and iron, with decorations associated with nature, modernity or exoticism. They were built in response to the local mining boom, underlining the mutual influence that existed with the neighbouring city of Cartagena.

Víctor Beltrí and Pedro Cerdán were the greatest exponents of Art Nouveau in La Unión. They designed various buildings, including Casa del Piñón, the Rentero building, the old Public Market, El Progreso building, Casa Cortés, Casa de Celestino Martínez or Casa del Tío Lobo de Portmán, all of which still exist today as a legacy of their era.

The Casa del Piñón building was built in 1905 by the architect Pedro Cerdán. It was awarded BIC (Asset of Cultural Interest) status in 1987 and can be listed in the Art Nouveau/Eclectic category. It is a three-storey, L-shaped building, with each façade level designed differently. The building was completely refurbished by the architect Martín Lejárraja and has served as the headquarters of La Unión City Council since 2008.

The old Public Market has hosted the prestigious International Cante de las Minas Flamenco Festival since 1978. It was granted BIC status in 1975 and can also be listed in the Art Nouveau/Eclectic category. The building was designed by the architect Victor Beltrí in 1903 and supervised by Pedro Cerdán, with its completion in 1907. The structure is in the shape of a Latin cross, but with arms of different lengths. An octagonal metal roof resting on a slender cast iron structure rises at the point where the arms cross. The pillars of the building are crowned by pointed shapes emerging from plant motifs that accentuate the structure's uniqueness and monumentality.

Casa Cortés is a two-storey building arranged around three axes, with cast-iron balconies and curved railings in three sections that round off the composition. Its construction dates back to 1906, designed by the architect Víctor Beltrí, in Calle Mayor de La Unión, commissioned by Pascual Conesa Martínez. It is a great example of local Art Nouveau with Catalan roots and was restored in 2016.