When planning a trip to Peru which involves Machu Picchu, you're average adventurous person has the Inca Trail in mind, and this was the case with us ... up until Gap Adventures decided to cancel two thirds of my 7-week honeymoon plans!
I'm glad to say this misfortune turned into our windfall after I rebooked a more obscure trek on the Salkantay Trail with 'Adventure Life'. This lesser-known variant takes 7 days (compared to the 4 of the Inca Trail) and traverses the challenging Salkantay mountain pass at 15,908 feet (4849m). You join the busy Inca Trail on day 5 of the combined trip, a quarter of the way along (i.e. skipping the first day of the Inca Trail).
The first four days of the Salkantay Trail were the highlight of the Peru trip. Poor Machu Picchu pales into relative insignificance compared to the trekking in the middle of nowhere, magnificent mountain backdrops and six horses for company carrying our heavy camping equipment. Our recommendation would be to do it quick before this secret gem becomes popular and well trodden.
[Note: We read recently that the Salkantay Trail may be losing some of its lustre - presumably some tour groups not cleaning up after themselves - worth enquiring about before booking a trip]