Victor Baltard and Henri Labrouste, two Parisian architects who led parallel careers in the mid-19th century, are currently both the focus of major exhibitions. The Musée d'Orsay has chosen the work of the former, probably better known because he designed the pavilions at Les Halles, Paris's former central market stupidly demolished in 1972. Meanwhile the Cité de l'Architecture et du Patrimoine is featuring the work of Labrouste, who designed an extension to the old Bibliothèque Nationale.
In their different ways, both shows are remarkable for their design and the documents they present. Depending on how familiar you are with the history of the various buildings and construction techniques, you may move smoothly from one venue to the next or perhaps take a break, to avoiding confusing from these two leading proponents of neoclassicism and metal structure. Together they give a fine understanding of this turning point in architecture, when traditional materials were replaced by cast iron.
Labrouste was the first to upset the certainties of his contemporaries, during his stay at the Villa Medici, after winning the Prix de Rome in 1824. He caused a controversy in France when he submitted a project to rebuild the Greek temple at Paestum, southern Italy. Dismissing the idea that the relics of antiquity were part of some universal tradition, he suggested that Paestum should be seen in the light of its context and historical moment. It may seem absurd today that this idea should have caused such a fuss, but many feared it might open the way for personal interpretation and hence extravagance.
Labrouste in fact took advantage of his four years in Italy to enlarge his understanding of ancient and in particular Etruscan architecture. Its influence is apparent in the Sainte-Geneviève library, on Place du Panthéon, completed in 1850. This masterpiece makes good use of both classical styles and open-work iron arches to achieve a huge reading room. His drawings are breathtakingly beautiful, whether he is bringing Pompeii back to life, or competing to build the tomb of Napoleon Bonaparte.
The design of Structure Brought to Light is perhaps over-precious but leaves sufficient room for Labrouste's legacy.
Baltard was also awarded the Prix de Rome, but he spent as much time on painting as he did on architecture. He too took part in the competition for Napoleon's tomb and won, but ultimately the job went to Louis Visconti.
In 1845 Baltard was tasked with building Les Halles. Three years later he was asked to supervise work on the capital's town hall and churches. In 1853, two years into construction, Napoléon III visited the site and was appalled to discover the monumental masonry facade Baltard planned to erect. The emperor demanded a complete rethink, with a clearer and more legible design, in keeping with prevailing styles in Britain. The great pavilions were completed in 1870 and operated without alteration for almost exactly a century. Only one building has survived, with its characteristic metal structure and masonry cladding. Reassembled in Nogent sur Marne, it now serves as an arts venue. But the legend of these huge buildings, and all that went on there, lives on as a tribute to how the project fitted into Haussmann's redesigned city.
To avoid the use of tie-bolts, which he considered unreliable and unsightly, Baltard chose large triangular metal brackets to keep the structure rigid. A fine designer, with an eye for ornamentation, he paid particular attention to the cast-iron components.
The Iron and Paintbrushexhibition underlines his dual concern for structure and decoration. It brings together an impressive series of documents – paintings, drawings, photographs and even a scale model of a pavilion – to enlighten contemporary builders. Much as Labrouste, many chose to follow Baltard's example.
Henri Labrouste – La structure mise en lumière is at Cité de l'Architecture et du Patrimoine, Paris, until 7 January. Victor Baltard – Le fer et le pinceau is at Musée d'Orsay, Paris, until 14 January
• This article appeared in Guardian Weekly, which incorporates material from Le Monde