Built beside the Mare River beginning in 1639, the octagonal Reformed church was designed by the city's architect Arent van 's-Gravesande, with advice from Jacob van Campen. Construction took ten years, with the stone entrance completed another ten years later. The church served the growing population on the north side of town, as Leiden's textile production expanded with thousands of weavers producing world-famous cloth in the later 17th century. Although the octagonal plan is frequently explained as logically deriving from Protestant emphasis on preaching, such an idea is probably an oversimplification. The first major central-plan church in the Low Countries is the magnificent seven-sided baroque Roman Catholic pilgrimage church of Onze Lieve Vrouw van Scherpenheuvel (Our Lady of Montacute) in Belgium, from 1609. In what is clearly a conscious rejection of the Counter-Reformation emotionalism of Belgian Baroque church architecture, Dutch designers based their forms on 16th-century Italian architectural handbooks that presented the ideas of antique Rome as interpreted in the 15th- and 16th-century Italian Renaissance. The result in the Marekerk, in Amsterdam's Westerkerk, and other Dutch "classical" churches is a space whose absence of emphatic decoration by default creates a focus on the spoken word. But simplicity is relative, as the fine carving of the facade of the Marekerk proves.