Located in the pretty town of Woodstock, Blenheim Palace makes a great excursion from nearby Oxford (which by the way is a fantastic city with many outstanding museums and colleges). What strikes a visitor immediately is its massive size, much bigger than many more famous palaces and probably only rivalled in size by Versailles. The interior is also quite impressive, but no so outstanding. They make a lot of their connection to Churchill (with an interesting exposition), but of course the major attraction is the 18th-century architecture and design. Even though I liked the palace more than I would have thought, I found the huge gardens even more impressive. They were designed by Capability Brown and include a large artificial lake (with a waterfall), a rose garden, and many other features. Seeing the palace and the garden takes at least half a day, especially on a nice summer day (which means huge crowds as well), but is certainly worth your time (even though the entrance fee is quite steep). There are good bus connections from Oxford.