Bordeaux is a great city to visit - it's a lovely, smaller version of Paris (much of Paris was designed after it's 18th century design), but many come to learn more about the wine culture of Bordeaux. If you only have one day, there is plenty to explore in town. I'd invite you to spend at least two, because visiting a producer outside of town is a must, be it the famous Chateau Pape Clement which is accessible by public transport or the intimate, family owned producer of Chateau Beard la Chapelle in the hills near Saint Emilion.