The Classic Inca Trail in Peru is well known as one of the world’s most famous hiking trails. The Inca Trail begins in the Sacred Valley of the Urubamba River and ends at the mystical and stunning ruins of Machu Picchu. The trail itself winds for 45 km (27 miles) through the Andes, a range of high high altitude mountains and dense subtropical cloud forest as well as gorges and valley floors.
Most people say you need to be in relatively good physical condition to hike the Inca Trail. It's not that the hike itself is extremely difficult, but it is more the altitude rising to over 12,000 feet that you need to prepare for before, and while traveling the Inca Trail. A good idea is to spend a couple of days acclimatising in Cusco, a mid altitude area, checking out the local culture and sights, before ascending to the higher altitude zones.
When is the best time to go? Well that depends on whether you want to enjoy a lush and green landscape, in which case May is a great time to go. The raining season leaves the ground soaked, so you can enjoy spectacular green embed views from Machu Picchu as well as along the trail. Peru’s dry season starts in May and goes through until September. It is important to note that the most popular season almost means you'll be encountering the largest crowds. So if you are wanting to enjoy the Inca Trail wit less crowds, then traveling there during Peru’s wet season (October through to April) is the time to go, and there will be no shortage of water, which can be a consideration during the dry season. 
If you want to know more about the Inca Trail itinerary - or compare it with the less crowded, but much more culturally immersive Lares Trail, check out our Inca vs Lares trail page.