In the second half of the 17th century, Amsterdam experienced an influx of Ashkenazim, Jews from Central and Eastern Europe. Jews often fled the pogroms in those areas. The first Ashkenazis who arrived in Amsterdam were refugees from the Khmelnytsky Uprising in Ukraine and the Thirty Years' War, which devastated much of Central Europe. They not only founded their own synagogues, but had a strong influence on the 'Amsterdam dialect' adding a large Yiddish local vocabulary. Despite an absence of an official Jewish ghetto, most Jews preferred to live in the eastern part of the old medieval heart of the city. The main street of this Jewish neighbourhood was the Jodenbreestraat. The neighbourhood comprised the Waterlooplein and the Nieuwmarkt. Buildings in this neighbourhood fell into disrepair after the Second World War; a large section of the neighbourhood was demolished during the construction of the metro system. This led to riots, and as a result the original plans for large-scale reconstruction were abandoned. The neighbourhood was rebuilt with smaller-scale residence buildings on the basis of its original layout.