On block six of Belén is the city's most important and historic architectural complex, almost entirely constructed of volcanic stone. Dating to the 18th century, it includes a church and colonial women's and men's hospitals, now housing ancient medical and archaeological exhibits. The entire complex is run by the National Institute of Culture. On a small and pretty square, the Iglesia Belén might be the most extraordinary work of colonial architecture in Cajamarca. The church, which replaced a primitive adobe-and-wood church on the spot, was begun in 1699 and completed a half-century later. Its decorative baroque stone facade is one of the finest in Peru. The interior is replete with delightful and large, carved polychromatic figures of angels and warriors; the carved pulpit is particularly impressive. The richly decorative cupola, supported by eight almost cartoon-like cherubs, was painted by highland natives.

The Hospital de Hombres (Men's Hospital) is located on a lovely courtyard marked by a fountain. The austere hospital, run by Franciscans, began receiving patients in 1630. So that they could focus on prayer, the patients' beds faced the altar and the Virgen de la Piedad. To the right of the entrance is a gallery of vibrant paintings, several of them portraits of highlands campesinos, by Andrés Zevallos. Across the street is the Hospital de Mujeres (Women's Hospital); on the facade, note the woman with child above the portal and, on either side of it, female figures with four breasts, symbols of the valley's super-potent fertility. Today the building houses perhaps the most interesting component of the Belén complex, a Museo de Arqueología y Etnografía, well laid out and exhibiting textiles and ceramics dating from as far back as 1500 B.C., replicas of Moche vessels, and local artisanship, dress (including Carnaval costumes), and silver milagros (prayer fetishes).