Stalking big game with a camera, hiking to one of the world's most spectacular waterfalls, exploring Mayan ruins that date to antiquity-- these and other adventures can be had at national parks around the world. And who better to tell you which ones to visit than people who've worked in national parks all their lives?

The 700-member (U.S.) Coalition of National Park Service Retirees has released a list of members' 10 favorite international parks for those considering their next global exploration.

Four of their choices have been visited by Post-Gazette writers, who offer their impressions. The remaining picks follow.

In 2006, I'd read a guidebook billing Tongariro National Park as having the greatest one-day hike in the world. I was sold.

The hike spans 17 kilometers, climbs a mountain and lasts at least six hours. Tour companies offer drop-off and pick-up services at either end of what is known as the "Tongariro Crossing." Ours picked us up before dawn at our hotel in the town of Taupo.

The start of the crossing is barren and otherworldly, with only a few yellow flowers coloring the rocky landscape. It's what Mordor looks like in the "Lord of the Rings" trilogy, which used a nearby mountain for filming.

Supposedly, from the top of Tongariro on a clear day, you can see all the way to New Zealand's South Island. I wouldn't know. By the time we got to the top, we were in a heavy snowstorm that had me nearly crawling along the ridgeline. I couldn't see 3 feet in front of me.

But as we descended, passing by emerald mountain lakes, warm volcanic rocks and a dense rainforest, I stripped down to a T-shirt and shorts.

And that's the beauty of Tongariro -- the physical challenge, the unlimited variety of landscapes and the ability to wake up and go to sleep in the same hotel room. Even with the terrible weather we had, I wouldn't hesitate to do it again.

-- Anya Sostek

In my opinion, safaris are too often taken in excessive luxury -- 600-threadcount sheets, expert guides leading guests right to the animals and chefs catering to every whim.

But in Kruger, you can take a safari on the cheap, like the locals do. I went to the 7,300-square-mile game reserve, the largest in South Africa, in 1999. We paid for one guided night drive, during which we saw a black rhinoceros, but otherwise drove the park by ourselves, spending hours squinting into the bush for hints of movement. We saw an elephant within the first five minutes and easily spotted lions, Cape buffalo, giraffes and antelope.

At night, we camped in what my husband called "reverse zoos." Humans stayed in fenced areas while animals roamed the rest of the park. Sometimes, though, the animals breached the divide.

While we were cooking dinner over a campfire, a monkey hopped over the fence and made off with our block of cheese. At night, the yellow-green eyes of hyenas glowed as they paced along the fenceline. And one morning we awoke to find a kudu -- a large antelope with spiraled horns -- romping amid the tents.

-- Anya Sostek

This park, encompassing 167 acres of subtropical forest spanning the border between northeast Argentina and southern Brazil, offers visitors a jungle gym of trails and overlooks that open to breathtaking waterfalls. The Iguazu River snakes in a U-shape and widens to nearly a mile within the park. A guided all-terrain vehicle ride offers a look at the history of the park and its immense biodiversity; a speedboat trip into the gush of one of the 275 waterfalls will soak the more adventurous travelers.

For the others, just the walk is enough. Allow at least two days to explore the stairways, walkways and small bridges that open into balconies, where gawkers squint and smile in the spray as the curtains of water crash close behind.

The uppermost level of trails places at eye level the park's centerpiece: the Garganta del Diablo (Devil's Throat), a 262-foot-tall semicircle of cascades wider and taller than Niagara Falls. An eco-friendly train transports visitors along a five-mile track to the Brazilian side for a panoramic view.

The joy of Iguazu is in its sense of surrealism: some outlooks feel nearly disconnected from the land. Butterflies dance along the trails, and nearly every picture taken on a sunny day includes a rainbow. It's a majesty that shouldn't be missed.

-- Megan Barrow

When we were visiting the small country of Belize in the summer of 2006, we debated whether it was worth a quick day trip across the Guatemalan border to see Tikal, the largest excavated Mayan site in Central America. It was well worth the trip. This magnificent World Heritage site, which means "Places of Voices," spans 222 square miles and until recently was mostly buried under the jungle.

It also has a Pennsylvania connection. The city, once home to 100,000 Mayas, was abandoned more than 1,000 years ago for unknown reasons. It was rediscovered in 1848 by a gum collector. Word spread and eventually archaeologists from the University of Pennsylvania led a major excavation of the site from 1956 to 1970. Many artifacts are now on display at the university's archaeology museum in Philadelphia.

The essentials: Wear comfortable shoes with rubber soles and hire a guide to get the most out of your visit. If you're in shape, you'll want to climb the very narrow, steep steps to the top of Temple IV -- about 230 feet -- to get a panoramic of the other temples peeking out above the jungle. There's much more to see than what you can fit into a day. If you're really into Mayan history and culture, stay several days.

-- Virginia Linn

Kakadu, Northern Territory, Australia

This World Heritage Site is jointly managed by the Aborigines and the Australian government. It has magnificent vistas, great waterfalls, stunning displays of Aboriginal rock art, and is habitat to an awesome predator, the estuarine (saltwater) crocodile.

Snowdonia, Wales, Great Britain

Snowdonia is a lovely mountain park, with Mount Snowdon, highest peak in Wales, rising to 3,560 feet. While this park is not geologically or scenically spectacular compared with many mountain parks, it is peaceful and beautiful in its own right.

Sagarmantha, Nepal

Sagarmantha, or "goddess of the sky" in Nepali, includes Mount Everest, the world's highest mountain, among other prominent peaks. It has distinctive wildlife and small picturesque Sherpa villages with their gumpas, or monasteries.

Madain Saley, Saudi Arabia

This region, the Biblical Midian, is mostly undulating desert, interspersed with huge rocky outcroppings and lush oases. Here, between 500 B.C. and 100 A.D., the same Nabatean people who carved the great structures of Petra, Jordan, created 125 monumental cut-rock tombs and facades, edifices up to 130 feet tall, still standing today in remarkable preservation.

Plitvice Lakes, Croatia

Halfway between Zagreb and Split, Plitvice has mountainous terrain, small lakes, streams and beautiful waterfalls. Crystaline deposits of travertine make for distinctive blue-green colors and exceptionally clear water. Excellent hiking trails abound, and quiet, nonpolluting electric ferries connect some paths. The vegetation makes fall "color season" especially spectacular.

Hortobagy, Hungary

Located on the "puszta," or great Hungarian plains, Hortobagy is also a biosphere reserve and a World Heritage Site. The plains and wetlands reflect two millennia of human occupation and have supported agrarian life for centuries. The area has several endangered bird species and is a refuge for the Przewalski horse and migratory waterfowl.