Gianni Bernardi and the LOFAR EOR collaboration The cosmological 21 cm line promises to be an essential tool for investigating the epoch of reionization of the Universe. The biggest challenge for its detection is the presence of foreground emission which is orders of magnitude stronger than the cosmological signal. We report here on a survey of selected sky fields observed with the Westerbork telescope with the purpose of characterizing the foreground properties for the cosmological 21 cm line.