Mosaics were a popular way to decorate churches in Italy in the Medieval period. They were not popular in England, France, Germany and countries of Northern Europe because they preferred to use stained glass windows as decoration. In Italy, the most famous church with its interior decorated with mosaics is St. Mark's Basilica, Venice. At Westminster Cathedral in London, (which is built in an Italian style) the mosaic decoration which was started more than 100 years ago is still continuing, bit by bit. Many of the mosaics at St. Mark's and Westminster Cathedral have gold backgrounds. 