Inca Highlands

Fly into Lima, and spend the night: flights to Cusco largely depart in the morning, to have daylight and to leave time for delays. Start taking ACZ one day before ascent (day of travel or first day in Lima), or two if high-risk.

Consider spending a day in Lima, particularly after a long flight: it's an interesting city, but not your focus.

Fly to Cusco, then on arrival immediately transfer to the Sacred Valley (optional but highly recommended). Take it easy, and enjoy rest and nature. Sleep the night in the valley, acclimating to altitude and enjoying the setting. Following day, see some sights in the valley, then either proceed to Cusco or spend another day in the valley (to acclimate further and see more sights). You can also take day trips to the valley from Cusco.

Cusco is the center of Inca culture: it has much to offer, and is the ideal base for trips to surrounding areas. Take the first day easy, spend at least two nights to acclimate to the altitude, and enjoy the city and surrounds. If you sleep in Cusco for your first night at altitude, you have a high risk of altitude sickness: taking ACZ is encouraged, and you should take it very easy.

There are many options for the trek, the focus of this itinerary.

The Inca Trail itself has many variants. Typically you'll take rail or road to the trailhead, starting from km 82 (or km 77 or 88, which require a bit more walking), and then spend 4 days/3 nights on the trail, with an optional extra day and night in Aguas Calientes (5 days/4 nights). There is also a 2 day variant from km 104 that just hikes the end of the trail, through the sun gate.

Alternative treks have much to recommend them: they are less crowded, more unique, more varied (different sights, longer or shorter, more or less demanding), do not require advance reservations, allow pack animals (mules, horses, or llamas), and are significantly cheaper.

The three main alternatives, in increasing order of difficulty, are:

• Lares valley trek from the Sacred Valley, which is lower altitude and easier (flexible, 4 days typical).

  This can end at Ollantaytambo, from which one can continue to Machu Picchu by rail.

• Salkantay trail, via Mount Salkantay (5 days, 75 km, max 4600 meters)

  Same area, but higher and somewhat more demanding than the classic Inca trail. Starts in Mollepata, ends near Machu Picchu at Santa Teresa or Hidroelectrica (the hydroelectric dam), from which one can continue to Machu Picchu by short hike or rail.

• Via Choquequirao (similar site to Machu Picchu, ruins bigger and much, much less touristy) to Machu Picchu (8 days, demanding trail)

  Starts in Cachora, 2 day hike to Choquequirao, then either return, or continue on a long, demanding hike to Machu Picchu, ends at Santa Teresa or Hidroelectrica, like the Salkantay trek.

These treks do not go through the sun gate and descend into Machu Picchu, however: they enter from below, by the town. Other treks simply enjoy the mountains, villages, and wildlife.

There are variants of these, often with idiosyncratic names, or named for a village, mountain, or pass, like "Cachiccata trek", village near Ollantaytambo, basically west/final end of Lares valley trek; and "Ancascocha trek" (variant of Salkantay trek, named for pass).

More distant treks, not in the Machu Picchu area:

• Ausangate trek (5 to 7 days), in mountains east of Cusco (opposite direction from Machu Picchu).

Machu Picchu is the highlight of the trip, though when you arrive, how long you spend, and which side trips you do are variable.

It is possible to return from Machu Picchu the afternoon or evening you arrive, particularly if you arrive early (4 day/3 night trek), but it is more relaxing to spend the late afternoon at the site (after others have left), and the night in Aguas Calientes (5 day/4 night trek). This gives you a rest after the trail, and allows you to see it early the next day, all rested and less crowded.

Ollantaytambo is the main alternative Inca ruin: it is easily reached from Cusco, it is the end of the Lares valley trek, and it is on the way to Machu Picchu by road or rail, so it can also be seen on the way to or from Machu Picchu.

Choquequirao is similar to Machu Picchu, but much less famous; it is also in the mountains, and can be reached by a trek.

There are numerous other sights in the region.

The Q'eswachaka bridge is the last remaining Inca rope bridge, and is renewed annually in June. It spans the Apurimac River near Huinchiri, in Canas Province, south of Cusco, and is becoming a minor tourist attraction.

On the way back from Machu Picchu, you can stop at various sites in the Sacred Valley, notably Ollantaytambo; see Ollantaytambo#After_Trekking_to_Machu_Picchu.

Consider spending a day in Cusco or Lima on return: this also leaves a day in case of delay earlier on. However, you've probably seen enough of Cusco while acclimatizing, and ending with Lima is a bit drab: go straight home from Cusco.

The most serious issue is altitude sickness: Lima starts at sea level and does not rise high, while Cusco is at high altitude (3,400 m). About 50% of people who fly from Lima and spend that night in Cusco suffer from altitude sickness, sometimes severely. The Inca Trail is higher still, going up to 4,200 m, and sleeping around 3,600 m, while Machu Picchu itself is not very high (~2,400 m), and the Sacred Valley is significantly lower than Cusco, though still at altitude (~2,800 m). The biggest danger is ascending rapidly, and the main solution is to ascend slowly. The main issue is breathing at night, so the altitude at which you sleep is what causes sickness, and conversely helps you acclimate. Thus, flying into Cusco and spending the night there will likely cause sickness, and flying into Cusco and immediately hiking the Inca Trail is idiotic.

To prevent and reduce altitude sickness, fly into Cusco and immediately transfer to the Sacred Valley, which is an ideal altitude to acclimate: spend a night or two there. Proceed to Cusco, spend two nights acclimating, then hike the Inca Trail. There's still a risk of altitude sickness, but less, and milder. Also, take it easy the first days at altitude, and drink a bit more water (an extra liter), and less alcohol (which dehydrates). In case of emergency, descend (drugs and oxygen can help, but descent is the best solution).

For extra safety, you can take acetazolamide (ACZ) before and during ascent, which jump-starts and speeds up acclimatization (it's the same biological mechanism): it's primarily for prevention (prophylaxis), not treatment. You generally need a prescription: check with a doctor. If you take it, expect increased urination (so drink more) and some tingling of the fingers and toes. If you have a history of altitude sickness, or are spending the first night at altitude in Cusco (instead of the Sacred Valley), you certainly should take ACZ, unless contraindicated. If you have no such history and are spending a night or two in the Sacred Valley, it is less necessary, but still prudent. Current CDC guidelines are 125 mg, taken twice a day (every 12 hours), starting the day before ascent, and continuing the first 2 days at altitude, or longer if ascent continues. Per this itinerary, that's day before ascent (in Lima or travel to Peru), then (most prudently) every day at altitude, due to repeated ascents (Cusco, Inca Trail, and low Machu Picchu back to high Cusco). You can discontinue use after highest campsite on trail, as it's descent after that, other than one optional low night in Aguas Calientes. 250 mg is more effective, but side effects are more likely: it's recommended if you are higher risk. If you have enough 125 mg pills, you can double the dose to 250 mg if necessary, so it's prudent to get more than the minimum.

You can also get a pulse oximeter to check your blood oxygen content to see how you're acclimating. Coca (in tea, chewing leaves, or candies) is a mild stimulant, and helps a bit with the symptoms (like coffee for a hangover), but doesn't help you acclimate faster.

On the off chance that you go scuba diving beforehand, wait at least a day before ascending: check with scuba shop.

Altitude sickness is unpredictable: there is no effective screening, and being healthy doesn't protect you; being unhealthy does add to the risk though.

The sun is strong and the air is dry: wear a broad-brimmed hat, UV-blocking sunglasses, long sleeves, sunscreen (SPF 30+), sun-blocking lip balm, and drink a lot of water. Use moisturizer if you like: the high altitude means water evaporates faster, due to the low pressure. Beware the sun even when cloudy: clouds don't block UV.

There are also general concerns for Peru (Peru#Stay safe and Peru#Stay healthy), particularly avoiding tap water (use bottled or boiled, even for brushing teeth); and for the Inca Trail itself (Inca Trail#Stay safe), particularly being in shape and equipped, and walking carefully, particularly on slippery wet stone.

Remember that the biggest danger when traveling is road accidents. Notably, have a local driver, and avoid driving at night: if moving locations, do it daytime, particularly morning or midday, not evening.

Since this is in the mountains, not the jungle, there is no need for a yellow fever vaccine. However, if you continue to Amazonia, this is recommended.