Primate researcher Dian Fossey famously became the first human to closely interact with mountain gorillas, sitting amongst their groups and getting up close and personal. The movie version of her book, Gorillas in the Mist, starred Sigourney Weaver and introduced people worldwide to this incredibly intimate wildlife experience, unlike any other in Africa — you cannot get out of the car and walk amongst lions or hippos.

Groups are led by one or more dominant big male gorillas like this one. They are known as silverbacks, because the hair on their back turns silvery white when they are fully grown adults. | Micato Safaris

Fossey did her work in what is now Rwanda’s Parc National des Volcans, a beautiful and misty national park on the slopes of the volcanic Virunga massif, spanning three countries including Uganda and the Democratic Republic of Congo. It remains the only place in the world to view these magnificent creatures, the largest of the great apes, in their natural habitat.

There are fewer than 1,000 of the threatened mountain gorillas left in the wild here. More than half are in this one Rwanda park, widely considered the best managed, with strict rules, well-trained rangers and trackers, and a permitting process that allows a maximum of just 96 guests per day to meet the gorillas. With growing demand from fast-developing economies such as China, Russia and Brazil, plus the traditional visitors from the U.S. and Europe, permits are becoming increasingly difficult to get, and earlier in 2017 the park doubled the already high price from $750 to $1,500 per person per day.

All the gorilla viewing treks include a hike of at least 30 minutes each way, often much longer, and are led by a ranger (in green) and accompanied by porters (in blue). | Micato Safaris

For most travelers, gorilla trekking is bucket-list experience, but because each interaction is so unique, and there are a dozen different groups in the park, a surprising number of guests double down and book two days of permits to maximize their visit. Many also add a day of Golden Monkey trekking in the park, which is much less expensive (under $100), and the other popular activity is a guided — and somewhat arduous — three-hour hike to Fossey’s grave. The region sits at or above 7,000 feet of elevation and all of the activities require at least a moderate level of exertion. One day of gorilla trekking typically involves at least two and as much as six hours of hiking at altitude over steep terrain, sometimes through thick jungle, and it is not recommended to those not physically prepared.

There are several lodges around the park headquarters, where all treks begin, and the most popular quality ones are the Sabyinyo Silverback Lodge and the Virunga Lodge. Renowned African safari lodge operator Singita is developing a new lodge here, but it’s not likely to open until 2018 or 2019. Because permits are so hard to come by, most travelers work around the dates they can get, and then take whatever lodging is available. Because the typical stay is just two to three days, most visitors combine gorilla trekking with a more traditional (and usually much less expensive) lower elevation African wildlife safari in nearby Tanzania or Kenya.

Gorillas are Rwanda’s national treasure, and every September there is a high-profile ceremony to name all the baby gorillas born in the previous 12 months, attended by the nation’s president and various dignitaries. This “gorilla” amphitheater has been assembled in the shadow of the Parc National des Volcans in preparation for the ceremony. | Larry Olmsted for USA TODAY

With the complex logistics, permits and convoluted ground transportation (the park is two hours from the airport in Rwanda’s capital of Kigali, all lodges require driving to the park welcome center, and then the actual treks begin 30-45 minutes away on four-wheel drive roads), using a specialty outfitter is mandatory. To plan an entire trip including permits, lodging and Kenya or Tanzania portions, consider Micato Safaris, jointly based in the U.S. and Nairobi and nine-time winner of Travel + Leisure magazine’s World’s Best Safari award, and five-time Conde Nast Traveler World Savers Award winner for its charitable and conservation efforts. If you want to get yourself to Kigali and use a local outfitter for just the gorilla portion, good choices include Primate Safaris and Thousand Hills Expeditions, both Rwandese-owned.

Some travelers visit the Uganda side of the massif, Bwindi Impenetrable National Park, where permits are less expensive but infrastructure less well developed, and the hiking is tougher. “Rwanda is much more accessible than Uganda,” said Steve Jermanok, owner of Boston-based boutique adventure travel agency ActiveTravels.com. “The hiking is less strenuous, the lodging options are growing fast, and you can do it all in as little as three days.”

Larry Olmsted, Special for USA TODAY

It takes a lot of veggies to keep the world’s largest great apes full, and mountain gorillas spend a lot of time eating. | Larry Olmsted for USA TODAY