The ancient Ecclesia Sancti Petri ad Ulmum, which has survived in its Romanesque form, arose 12km west of Milan along the Roman road to Novaria. It is first mentioned in a document of circa 1100 and was subsequently altered during the course of the following centuries. The first investigation, which it is hoped will lead to more extensive interventions, involved a geophysical survey and several trial trenches and identified structures of importance for the architectural definition of the monument. It also brought to light a stretch of an unknown pre-Romanesque building which may help to shed light on the earliest phases of the church of S. Pietro all’Olmo. A legend tells that during Diocletian’s persecutions the tortured but intact body of San Vittore was found, guarded by ferocious lions, in a wooded area called ad ulmos, situated along the road from Milan to Vercellas, as is in effect S. Pietro. It is evocative to imagine that a small Lombard church was later built on the site of the miraculous find. (Roberto Mella Pariani, Laura Simone Zopfi)

Following the first excavations undertaken in 2005, research continued providing new and exciting results especially from the identification of the archaeological remains of a domus of late Roman date. The structure was situated just north-west of the old church and traces of the domus were also found inside the church in a room used as the sacristy. Also present in this room, above the late Roman level, were wedged post holes probably relating to wooden structures of early medieval date. Also of significance is the fact that the structure of the so-called sacristy was originally built (c.1300) as a funerary chapel, probably destined for the burial of the chapel’s founder. In fact, a monumental masonry loculus was found at the centre of the structure, containing the skeletal remains of an adult individual. The deceased was positioned facing towards the base of an altar.

In 2010 the excavations inside the church were completed, the results of which documented its complex and interesting history. This covered a span of 1500 years beginning, between the Early Christian era and start of the early medieval period, with the reuse of a heated apsidal room belonging to a Roman villa. Following numerous alterations the church assumed its present Romanesque form, undergoing modifications in1500. In the 16th century Renaissance levels an unusual funerary ritual was documented, with infant burials in imbrices with offerings of food and coins. The particularity of the ritual and the anthropological analyses of the skeletal remains have raised interesting questions.