Another option, if the landscape environment must be used (i.e., if not the totality of the document shoud be in landscape format), is to use the titlesec package to imitate the Rejne style for chapters[1]. The code looks something like the following:
[1] In fact, the titlesec package allows the user to easily define the styles predefined by the fncychap package, and besides, you can create a wide variety of new styles.