Of all the industrial buildings built by Muncunill in Terrassa, the Aymerich, Amat i Jover factory is the most significant one, both for its dimensions and for the construction procedures used. It occupies an area of 15,000 square metres, of which 12,000 correspond to the large engine room. It is a large space with seven bodies arranged on cast iron columns and covered with flat brick vaults and braces. The nave receives light through openings oriented to the north, which adopt a sawtooth arrangement. Each turn is of circular generator and arbitrary directive. The guideline rests on two sections of the nave and is located on two arches, one recessed and the other elliptical. The generatrix draws a very lowered arc. The vault is bent to facilitate the insulation of the ship. Each vault is formed by three tiles and is separated by small brick partitions that leave an air layer of 15 centimetres. Each turn is held by straps of thirty millimetres in diametre. In this way, diffuse and equal lighting is achieved throughout the nave.

Vapor Aymerich, Amat i Jover is an old textile factory located on Rambla d'Ègara in Terrassa. It was built by Lluís Muncunill between 1907 and 1908, and it currently houses the Science and Technology Museum of Catalonia. It is considered the most important modernist industrial building in Catalonia; and its name is due to the use of the steam engine as the main source of power.

The original set consisted of a production warehouse, a three-body annex building intended to house boiler rooms, the steam engine room and the electrical workshop, the courtyard, the 42-metre-high chimney and the office building.

It is, therefore, a building intended for a woolen cloth textile factory with steam-based motive power. It consists of two independent bodies: the industrial unit, with the engine room, and the façade, with adjacent outbuildings that form the enclosure. The production building, with a rectangular floor plan, has 12,000 m2 and is covered by a peculiar roof in the shape of saw teeth. The usual straight forms of this type of roof were reformulated by the architect Muncunill with Catalan vaults resting on lowered and parabolic arches, which are combined with skylights. At the same time, they are supported by almost 300 cast iron columns, which also served as downspouts and as support for the mudguards, the contraptions that transmitted the power of the steam engine to all the machines in the factory.

The large nave with vaulted ceiling with sinuous guideline and circular generator stands out. The vaults project light through north-facing skylights, which are built with six layers of fine tile. The height of the ceiling is 6'50 metres. The walls are made of stone. The roof vaults are bold and aesthetic; they use modern (cast iron) and economical materials (tiles and bricks).

It has a large room for boilers and another for electricity. There was the "Compound" system steam engine made by the engineer Francesc Crespo, four large underground coal chambers and a chimney 41 metres high with an internal passage of 2'30 metres. It presents a large water tank made by Antoni Bruguera, of reinforced cement. The pavement is from Portland and the cement from Sant Joan de les Abadesses and Vallirana.

The fireplace is located in the courtyard and has a truncated cone shape, with hoops that reinforce the structure. The base is octagonal, with arches and mouldings; the crown has collars of different widths with glazed ceramics. The shaft is 35 metres high and has an internal step of 2.30 metres with a height of 7 metres.

The renovations to Vapor Aymerich, Amat i Jover have been carried out in several phases. Joan Margarit and Carles Buixadé, architects, were in charge of the main rehabilitation of the building. In a first phase, in 1984, the façade, the body of the steam engine and the boilers were restored. The layer of white lime was also removed so that the work could be seen.

In 1996, the second renovation was completed, incorporating a 2,200 m2 basement. With the third intervention by Quim Larrea and Francesc Patrís in 2000, the entrances were placed in the northern part of the complex. The building included the reception and the restaurant. A photovoltaic façade was also installed on the partition wall.

The steam factory was owned by Josep Aymerich i Grané, Francesc Jover i Barba and Pau Amat i Bogunyà, who applied for permission on January 25, 1907. The favourable report of the Development Commission came out on March 20 and agreement of the Consistory on March 26, 1907. The project was carried out by Lluís Muncunill. The façade is by the same architect, but informed already by the substitute municipal architect, Melcior Viñals and approved on January 17, 1908. In 1912, Francesc Jover died, and the widow decided to leave the Aymerich, Amat i Jover company.

The factory accommodated the entire wool transformation process. From 1920, the yarns moved to Fígols and the factory specialised in fabrics, renting its spaces to other companies.

With the floods of 1962, the building was badly affected. Finally, the factory closed in 1976. In 1983 the complex was bought by the Generalitat de Catalunya and adapted for a museum, according to a project by the architects Carles Escudé i Muncunill and Ramon M. Puig i Andreu.