Our next selection is largely unknown to tourists from the United States, and perhaps that makes it even more precious. The limestone caves of the Plitvice Lakes National Park make the water of its 16 lakes and a handful of waterfalls shimmer brilliant shades of turquoise, silver and green. And to get a better view the lakes' beauty, you'll find a web of wooden plank walkways scattered throughout. But note that there is no true best or worst season to stop by this site in central Croatia. Snow and ice transforms the area into a winter wonderland; in summer the surrounding trees further enhance the hues of the lake water. If at all possible, though, avoid the onslaught of local tourists in July and August.
Taj Mahal, India
Molded out of red sandstone and white marble, and sparkling with the glint of semi-precious stones, this mausoleum of northeastern India needs no justification to appear on our list. Frommer's says, "It's not just the perfect symmetry, the ethereal luminescence, the wonderful proportions, or the sheer scale," that makes us revere the Taj Mahal. It's also "the exquisite detailing covering every inch of marble that justifies it as a wonder of the world." Its amorous background also feeds our admiration: It was commissioned by a 17th century Mughal emperor to honor the memory of his favorite wife, Mumtaz Mahal. Consider planning a trip for sometime between October and March to behold Taj's majestic domes, chambers and minarets; that way the weather will be somewhat cooler for walking around. If you have time, stay from the early morning until the late night, as "the radiance of the Taj under the moonlight is beyond any explanation," notes TajMahal.org.uk.
Snorkeling in the Great Barrier Reef, Australia
Australia's luscious islands, cays and coral reef system of the Great Barrier Reef are awesome in scope and visuals -- in fact, this reef covers more of the world than any other entry on our list (approximately 135,000 square miles; the only living thing visible from outer space). All who encounter even a small portion of this gorgeous giant are dazzled by its aquamarine waters and honeycomb beaches. Even more beauty awaits you below the water surface: a maze of more than 2,900 spectacular coral reefs and countless marine life. Come to this area just off the coast of Queensland between June and October, so you can avoid the worst of Australia's oppressive heat.
Borobudur in Indonesia
The true origins of this impressive Buddhist monument, located in central Java, are somewhat disputed. According to the UNESCO World Heritage website, the Borobudur temple was founded by a Saliendra dynasty king sometime between 750 and 842 A.D. Still, you don't need a definitive history lesson to fully appreciate its grandeur. Just feast your eyes on its intricately sculpted gray-stone relief panels (slats of stone carved with artwork to depict the life of Buddha) and the perfectly symmetrical stupas (mound-shaped structures containing Buddhist relics). They're even more precious due to their resilience: Borobudur is still gorgeous despite nearby bombings and volcanic eruptions. Try to visit in May; that's when the air is supposedly the cleanest in Java. And plan your trek at sunrise or sunset to witness how the light catches the stupas' perforations.
Grand Canyon, United States
We have to root a little for the home team. And here in the United States, the astonishing depths and incredible sunsets of the Grand Canyon make it a shoe-in on this list. Plus you can enjoy the scenery while you work up a sweat, hiking the rigorous Bright Angel Trail or rafting the Colorado River. As President Theodore Roosevelt famously noted, this park is "one of the great sights which every American, if he can travel at all, must see." Many take Teddy up on his word -- so if you want to explore this northern Arizona park, we suggest you avoid the staggering crowds of the summer. Consider visiting between March and May or September and November, when the weather is pleasant and the lodging rates are reasonable.
The Palace of Versailles, France
The Palace of Versailles might have had humble beginnings, but times have changed. Now, this ain't no simple hunting lodge, but rather an opulent tribute to the former French monarchy. Highlights include the reflective Hall of Mirrors, where world leaders met to sign the 1919 treaty that ended World War I; the manicured French-style gardens, which prominently feature the iconic Bassin d'Apollon (fountain) and the verdant Orangerie garden; and the Petit Trianon, a smaller chateau gifted to the infamous Marie Antoinette by her husband, King Louis XVI. Early summer is idyllic in the Île-de-France region, so plan your sojourn for that season. That's also when you'll find a few music concerts and special events taking place in the Versailles gardens.
Machu Picchu, Peru
Machu Picchu's 12 acres of mysterious temples and exquisite terraces are perpetually shrouded in cloud tufts, proving that this ancient site of Peru's Urubamba Valley still lives up to its reputation as the “Lost City of the Incas.” Or at least it seems like it from the pictures. In reality, this ancient city is always overrun with hikers exploring the Inca Trail or catching the view from the Temple of the Sun. So come with plenty of camera film and patience. For fewer crowds -- though not by much -- visit between October and April.
The Great Temple of Ramses II in Egypt
During his 67-year reign, Pharaoh Ramses II left many visual reminders of his greatness. Perhaps the best known are the four larger-than-life statues carved into a mountainside of southern Egypt. Many don't realize there's more to this site -- sometimes called Abu Simbel for the town you'll find it in -- than those seated statues seated on the facade. Pass through them and you'll find more detailed statues and intricate hieroglyphs depicting the Egyptian army's victory over ancient Libya, Syria and Nubia. Next door is the smaller Temple of Nefertari, dedicated to the Pharaoh's favorite wife. If you truly want to be wowed, you should swing by Abu Simbel around Feb. 20 or Oct. 20. Twice a year around those days the sun's rays shine directly into the larger temple to illuminate the artwork and statues within.
Great Wall of China
Fiction: The Great Wall of China can be seen from outer space (with the naked eye). Fact: it is pretty fantastic to view up close and personal. It sweeps through approximately 4,000 miles of northern China, and different sections guarantee different tourist experiences: The jungly sections of Simatai and Jinshanling are good for hiking; the arresting and gorgeous Mutianyu stretch is good for snapping photos; and the crowded Badaling portion is good for convenience (it's only an hour away from exciting Beijing). Plan your trip for anytime (just imagine the contrast of the Great Wall with the white snow of winter, the red leaves of fall and the green grass of spring and summer), but do try to bypass the hordes of tourists that visit on the weekends year-round.
The Northern Lights in the Arctic Circle
This scientific phenomenon occurs when charged solar particles collide in the earth's geomagnetic field and create a colorful, magnificent glow in the sky's upper atmosphere. According to the Huffington Post, "ideal viewing conditions are crisp, cold, clear and cloudless skies with little light." And though it is possible to see the Northern Lights in other parts of the globe, this phenomenon is most prevalent in the world's polar regions; the name Aurora Borealis refers to the lights as seen from northern latitudes (Aurora Australis is the name for the lesser-known Southern Lights of the South Pole). For the best viewing, Fodor's recommends visiting Anchorage, Alaska or Calgary, Alberta. You can also see the Northern Lights in parts of Denmark, Finland, Iceland and Russia, among other countries. (S)