Machu Picchu is the granddaddy of archeological sites. Set in the Andes Mountains, the site was once an estate for the Inca emperor, as well as a place of worship and education. When the Spanish conquered Peru, Machu Picchu was abandoned, and the colonists never learned of its existence. The site remained hidden in the Andes, shrouded by green mountains and clouds of mist, completely unknown to the outside world.It wasn't until Hiram Bingham III, a Yale historian and explorer (and the inspiration for the famous character Indiana Jones) uncovered the ancient site in 1911 that the world took notice.And what notice it was. Machu Picchu's visitor numbers grew quickly, as did its aura. It soon became Peru's largest driver of tourism. Movies were made, books were written. Artifacts were taken, then returned. Machu Picchu was even recognized as one of the new seven wonders of the world, an honor that all but solidifies its place on the bucket lists of intrepid travelers around the world.But all this popularity has taken a toll.With 2,500 visitors per day wandering around the sacred stones, the temples are starting to topple. Structures that held for more than 500 years through earthquakes and landslides are coming apart. The site is under UNESCO protection, and in 2011 the Peruvian government limited the number of visitors allowed each day. Some have called for stricter rules, such as making areas off limits or requiring all visitors to stay with a guide. The future is unknown but one thing seems inevitable; it may not always be possible to visit the ancient city the way you can today. Here's what you need to know to before visiting Machu Picchu.Plan AheadThe best time to visit Machu Picchu is between May and September, when the weather is dry. This is also the most popular time at the site, and tickets and trains can sell out far in advance. October through April are considered“off peak, as it's rainy season, but crowds can be thinner.As soon as you know when you want to go, book your tickets. You can buy tickets online through the official Machu Picchu portal. The online system can be tricky to navigate, however. Pay a little more and you can have an agency take care of tickets for you. Or you can pick up tickets in person in Cusco, but keep in mind that tickets sell out weeks in advance during peak season. Also, keep in mind, if you're planning to hike the Inca Trail, your tour operator will take care of your tickets for you.It's possible to see the whole site in one (long) day; take the train in the morning, spend your day at the site and return that evening. If you want to climb one of the nearby mountains or be one of the first at the site in the morning, spend a night in Aguas Calientes, the town at the base of the mountain. The town itself has plenty of tourist kitsch, with pizza parlors, souvenir shops and bars hawking three-for-one pisco sours. It's also a good place to recoup or get a massage after an Inca Trail hike, but otherwise, there's little reason to linger.Getting to Machu PicchuMost visitors to Machu Picchu arrive by train, either from Cusco (via the nearby Poroy station) or the Sacred Valley. The train from Cusco takes nearly four hours; from Ollantaytambo, the train takes approximately two hours. You can buy tickets ahead of time online, which is highly recommended as trains tend to fill up in the busy season. Trains arrive in Aguas Calientes; from there, you'll hop on a 20-minute bus ride that snakes up to the entrance.But if Machu Picchu is the Holy Grail, hiking the Inca Trail is the true pilgrimage to get there. The ancient path is a challenging four-day trek. All trekkers must go with an organized group or guide; Llama Path and Alpaca Expeditions are popular, reputable options. While the trail sees about 400 hikers a day, this is not a stroll in the woods. Be prepared for the hot sun, cold nights, and lots of stair climbing at high elevations (the highest point ascends more than 13,700 feet). Also keep in mind that if you want to do the trek, you'll need to book your spot five to six months in advance, sometimes earlier during the peak season, and note: the Inca Trail is closed in February.Exploring Machu PicchuOnce you've arrived, you can hire a guide or explore on your own. You can easily spend a full day discovering the urban core, temples and agricultural zones. High above the site is Intipunku (or the Sun Gate), where hikers on the Inca Trail arrive. All others arrive via the main entrance and make their way across cultivation terraces to the urban area. At the far end of the site is the trail to Huayna Picchu, which offers striking views of Machu Picchu.Climbing Huayna PicchuFor a different perspective over the site – and a test of your comfort with heights – climb Huayna Picchu, that iconic pyramid-shaped mountain often captured in Machu Picchu photos.You'll need a separate ticket to climb the peak, and entry is limited to two time slots each morning. It takes about 45 minutes to reach the top, a craggy pile of rocks overlooking the Andes, Machu Picchu and the Urubamba River. The shortest way down is also the most treacherous; you'll traverse the panic attack-inducing Death Stairs, which lead straight down into what looks like oblivion. A less harrowing (but more physically demanding) route leads around the mountain past the Temple of the Moon, which takes about two to three hours. Either way, get ready to feel your legs burn.