The best known of the myriad archaeological ruins near Tarma, this was the capital of the Taruma culture and later a major Inca administrative center. The fairly extensive remains include storehouses, palaces and an impressive, still-used aqueduct system. Unlike other Peruvian places with the suffix 'tambo,' this really was a genuine tambo (Inca way-station camp). Tarmatambo is 6km south of Tarma.
Ask at the tourist office about guides to take you there and to other sites: going solo, these ruins are difficult to find. Independent travelers can take a Jauja-bound bus to Tarmatambo village on the main road below the ruins.
From Tarmatambo, a rarely used Camino del Inca (Inca road) forges over the hills down to Jauja: there's basic accommodations in Tarmatambo but it's then a strenuous (but beautiful) all-day hike to Jauja (40km).