When the interior designer Olga Polizzi opened the Hotel Endsleigh, in the Dartmoor National Park in the Devon region of southwest England, she had one goal in mind. She wanted it to “feel like staying in a friend’s house,” she says.

In this case, that friend happens to be the late Georgina, Duchess of Bedford, and her husband, the sixth Duke of Bedford. That house was their country villa, conceived by the architect Jeffry Wyatville (whose other clients included King George IV) in the early 19th century. Now in its newer incarnation as a hotel, it welcomes guests from all over the world.

Proprietor Olga Polizzi uses colorful design to energize a serene environment.

Resplendent in its rusticity, Endsleigh has been likened in its spirit to the Queen’s Hamlet, the farm built by Marie Antoinette at Versailles. It’s little wonder that Hotel Endsleigh inspires such loyalty among its most devoted guests, some of whom visit five times a year.

Though relatively modest in its architectural proportions (there are just 21 rooms), it’s sequestered among 108 acres of gardens landscaped by the 18th-century designer Humphry Repton.

Is it teatime yet? At Hotel Endsleigh, such service is always available.

With lawns that slope down to the Tamar River, it has one of the most picturesque vistas in the country. Designed almost entirely around this rural panorama, it offers, at nightfall, the ultimate luxury in our over-illuminated world—a pitch-black sky with the occasional shooting star.

Polizzi—also the proprietor of the Hotel Tresanton, in Cornwall, and the Star in Alfriston, Sussex—saved Endsleigh from otherwise inevitable decline. When she first visited it, in 2003, it had been languishing on the market. Coaxing the interior back to life, in close collaboration with English Heritage, was a huge undertaking, beginning with installing heating and functional bathrooms. This year, it celebrates its 20th anniversary.

It’s tempting to stay inside and enjoy the views, but when the weather cooperates, nothing can rival Endsleigh’s gardens.

Polizzi preserved—and carefully restored—many of the home’s original wallpapers and furnishings. The result is a wonderfully understated and deeply comfortable take on English-country-house style. The hotel is adorned with antiques and curiosities, and there are open fires at every turn and many places to sit and consume that view. (The hottest seat? The floral chaise in the window of the well-stocked library, in close proximity to the bar.)

Wonderfully old-school in its atmosphere, the hotel offers activities that include croquet, riding, and fishing. Afternoon tea is a daily ritual and is served in the paneled and coat-of-arms-lined dining room. Mealtimes, courtesy of head chef Thomas Ewings, retain a sense of occasion and romance. “Our main goal is for people to feel looked after and embraced,” says Polizzi.

A little bit of drama is always welcome, whether it’s found on a grand walkway or at a celebratory dinner.

The garden is arguably at its best in April and May, when the long drive and parterre are lined with radiant bursts of rhododendron. (Endsleigh has its own eponymous blush variety.) But even during mid-winter, in the soft, watery sunlight with mist rising off the river, it casts its own subtle spell. Exploring the lichen-wrapped woodlands, waterfalls, dells, follies, and grotto, encrusted in shells and corals, is a balm for the soul.

The writer was a guest of the Hotel Endsleigh, where rooms begin at $345 per night, including breakfast

Aimee Farrell is a Cambridge, U.K.–based writer and consultant specializing in design, interiors, and the decorative arts. She is a contributing editor at the Financial TimesHTSI