This will probably be the least romantic part of your visit to Machu Picchu. There is a shuttle that runs between the town of Aguas Calientes and the entrance to the ruins. They are full size green busses that have been privatized and are a monopoly. Consequently, charge high prices in US dollars. The bus costs $12 each way for a 20 minute bus ride.

There is a very reduced rate for locals, mostly for guides who live and work in Aguas Calientes. Perhaps this is the reason that they are so strict about their bus tickets. Whatever the reason, you must have your passport to buy your bus ticket and you can only use it on the day and for the direction that you paid for. Below is one of my bus tickets (on which I qualify for the local rate). You can see that it has my name, the date, my ID number, age, sex and even specifies if it’s an up or down ticket.