The reading room at the Sainte-Geneviève Library, a public and university library in Paris which contains around 2 million documents, including the collection of the Abbey of St Genevieve. The building was designed by Henri Labrouste and completed in 1850. Its 17-by-80-metre (56 ft × 262 ft) reading room, which reaches 15 metres (49 ft) in height, is noted for its slender cast iron structure.Photograph: Marie-Lan Nguyen