The Quartier Léopold was not an immediate success. Its development really only took off when the area was incorporated into Brussels in 1853 and the Conseil communal decided to extend the Rue de la Loi, the main link between the town and the suburb. But the original plan was much simplified, and the monumental centre was never realized. More attention was paid to architectural design when a new district—the Quartier NordEst—was added to the Quartier Léopold according to plans produced by the architect Gédéon Bordiau and approved by the Conseil communal in 1875, i.e. during the administration of Jules Anspach. Square Marie-Louise and Square Ambiorix, together with Avenue Palmerston linking them together, formed a grand complex of parks and squares—possibly slightly too large in relation to the urban structure surrounding it.7 A development in design thinking can be clearly discerned here, from the slightly static grid planning in the Quartier Léopold to the Baroque dynamism of the Quartier Nord-Est, which can be said to herald the more grandiose planning under Leopold II.8
Another much discussed planning issue concerned the Avenue Louise. At the end of the 1840s two land developers acquired a concession to lay out a new avenue from the ring boulevard to the Bois de la Cambre. The project was felt to be important, as it would link the town to a wooded area suitable as a public park. The two developers were not able to realize their plans, but following persistent pressure from the government and the promise of financial support, the town took over the enterprise and it became possible to complete this avenue, 55 metres wide and almost 3 km long. To compensate for its cost the town was also permitted—despite protests from the municipality of Ixelles—to incorporate the street and a zone extending about 40 to 100 metres on either side of it. Today Brussels still thrusts like a wedge into the neighbouring municipality. The Avenue Louise, lined on both sides by splendid mansions, soon became one of the most fashionable residential areas in Brussels.9
Ever since 1830 Brussels had been growing rapidly in both population and importance, and was well on the way to becoming one of the main commercial centres in Europe. But by the middle of the century its medieval street network was still intact, apart from the changes in the upper city mentioned above and a few minor adjustments in the low-lying districts. Thus, the first attempts at urban renewal comprising a number of properties was the construction of the shopping arcade Galeries St-Hubert (1836–45), one of the pioneers of its kind in Europe and still functioning today, and the long but rather narrow Rue Blaes cutting through the historic Marollen Quartier (1853–60).