Tarmatambo is the archaeological site that gives Tarma real depth. The terraces and stone buildings sit above the modern valley on a route tied to the Inca road network, and the setting makes clear why this was a useful highland stop between ecological zones.
The remains are not presented like a famous Sacred Valley site, so go for the landscape as much as the masonry. The walk also gives wide views back over the valley and the flower-growing land around Tarma.