Complex sentence: Martigny became the first bishop's seat in Switzerland and is today admired for its historical districts of La Bâtiaz and Vieux-Bourg featuring several churches and secular buildings worth seeing.
Split into simpler sentences: Martigny became the first bishop's seat in Switzerland. Today it is admired for its historical districts of La Bâtiaz and Vieux-Bourg which feature churches and secular buildings worth seeing.