9 Best Sights in The Thames Valley, England

More than half a million intriguing archaeological and anthropological items from around the globe, based on the collection bequeathed by Lieutenant-General Augustus Henry Lane Fox Pitt Rivers in 1884, are crammed into a multitude of glass cases and drawers. In an eccentric touch that's surprisingly thought-provoking, labels are handwritten and items are organized thematically rather than geographically—a novel way to gain perspective. Give yourself plenty of time to wander through the displays of shrunken heads, Hawaiian feather cloaks, and fearsome masks.

Attention all Muggles: this spectacular attraction just outside Watford immerses you in the magical world of Harry Potter for hours. From the Great Hall of Hogwarts—faithfully re-created, down to the finest detail—to magical props beautifully displayed in the vast studio space, each section of this attraction showcases the real sets, props, and special effects used in the eight movies.

Visitors enter the Great Hall, a fitting stage for costumes from each Hogwarts house. You can admire the intricacies of the huge Hogwarts Castle model, ride a broomstick, try butterbeer, explore the Forbidden Forest, and gaze through the shop windows of Diagon Alley. The Hogwarts Express section—at a faithfully reproduced Platform 9¾—allows you to walk through a carriage of the actual steam train and see what it's like to ride with Harry and the gang. Tickets, pegged to a 30-minute arrival time slot, must be prebooked online. The studio tour is a 20-minute drive from St. Albans. You can also get here by taking a 20-minute train ride from London's Euston Station to Watford Junction (then a 15-minute shuttle-bus ride, free with a valid Studio Tour ticket). Via car from London, use M1 and M25—parking is free.

Described by Queen Victoria as a "bijou of taste," Cliveden (pronounced Cliv-dn) is a magnificent country mansion that, for more than 300 years, has lived up to its Georgian heritage as a bastion of aesthetic delights. The house, set on 376 acres of gardens and parkland above the River Thames, was rebuilt in 1851; but it was the rich and powerful Astor family, who purchased it in 1893, that made Cliveden famous. In the 1920s and 1930s this was the meeting place for the influential salon known as the "Cliveden Set"—a group of strongly conservative thinkers who many accused of being Nazi sympathizers. Its doyenne was Nancy Astor, an American by birth, who became the first woman to sit in the British Parliament. The ground-floor rooms of the house are open, as is the Octagon Chapel, with its beautiful gilt-painted ceiling and wall panels. You can wander the lovely grounds, which include a water garden, miles of woodland and riverbank paths, a kids' play area, and a yew-tree maze. Book your timed ticket for the house beforehand or early on the day. Boat hire and trips are available daily in July and August. Note that opening times of the house can be unpredictable, even at the busiest times of the year; always call before setting out.

Founded in 1621 as a healing garden, this is the oldest of its kind in the British Isles. Set on the river, the University of Oxford's diverse garden displays 6,000 species ranging from lilies to citrus trees. There are a spacious walled garden, six luxuriant glass houses, including insectivorous and lily houses, and interesting medicinal, rock, and bog gardens to explore. Picnics are allowed, but you must bring your own food and drinks, as there's nowhere to buy them inside.

This highly decorative Victorian Gothic creation of cast iron and glass, more a cathedral than a museum, is worth a visit for its architecture alone. Among the eclectic collections of entomology, geology, mineralogy, and zoology are the towering skeleton of a Tyrannosaurus rex and casts of a dodo's foot and head. There's plenty for children to explore and touch.

Focusing on the history and sport of rowing, this absorbing museum built on stilts includes exhibits devoted to actual vessels, from a Saxon log boat to an elegant Victorian steam launch to Olympic boats. One gallery tells the story of the Thames as it flows from its source to the ocean, while another explores the history of the town and its famed regatta. A charming Wind in the Willows walk-through exhibit evokes the settings of the famous children's book.

This traditional event, which dates back 800 years, takes place in Marlow during the third week of July. By bizarre ancient laws, King Charles owns every single one of the country's swans (just as his mother did before him), so each year swan-markers in skiffs start from Sunbury-on-Thames, catching the new cygnets and marking their beaks to establish ownership. The King's Swan Marker, dressed in scarlet livery, presides over this colorful ceremony.

With exhibits on everything from food to burial practices, the Verulamium Museum, on the site of the ancient Roman city, explores life 2,000 years ago. The re-created Roman rooms contain colorful mosaics that are some of the finest in Britain. Every second weekend of the month, "Roman soldiers" invade the museum and demonstrate the skills of the Imperial Army.

Adjacent to the Verulamium Museum, this park contains the usual—playground, wading pool, lake—and the unusual—Roman ruins that include part of the town hall and a hypocaust, or central-heating system. The hypocaust dates to AD 200 and included one of the first heated floors in Britain. Brick columns supported the floor, and hot air from a nearby fire was drawn underneath the floor to keep bathers warm.