Inca Quarry Trek
aka Cachicata (3 days)
This trek goes through the mountains south of Ollantaytambo. It is not a single trail like the Inca Trail.
Different agencies may have slightly different routes. In general, the trek starts near Pacchar or the Perolniyoc waterfall. It may include a cave called Ñaupa Iglesia. The trail goes roughly northwest to the Sun Gate (below) that you can see from Ollantaytambo.
The quarry is where the Inca had stones cut to make the Sun Temple at Ollantaytambo. You usually spend the last night in a hotel in Ollantaytambo or Aguas Calientes, and visit Machu Picchu the next morning.
Agencies
For info on selecting an agency - see Cusco Trek Agencies