如何在乳胶中的一个文档中混合单列和双列？

I have a document and want to create it as a twocolumn-document. That works fine with the twocolumn-option at the documentclass-command. But I have some tables and images, that are too big and should be included using both columns. These tables and images should be mostly on the same page, so \onecolumn and \twocolumn is no option (with some exceptions). I tried the multicol-package, but strangely I lost my tables this way. So knows anyone another solution?I have a document and want to create it as a tw