One important reason was the need for alternatives to the expensive eastern trade routes that followed the Silk Road. Those routes were dominated first by the republics of Venice and Genoa, and then by the Ottoman Empire after the conquest of Constantinople in 1453. The Ottomans barred European access. For decades the Spanish Netherlands ports produced more revenue than the colonies since all goods brought from Spain, Mediterranean possessions, and the colonies were sold directly there to neighbouring European countries: wheat, olive oil, wine, silver, spice, wool and silk were big businesses.