An office building from the 1930s in London was about to be demolished — until remnants of the city’s first Roman basilica were found in the basement.

An rare discovery in northern Luxembourg has given historians a fresh glimpse into the final years of the Western Roman Empire. Archaeologists have uncovered a hoard of gold coins dating back to the late fourth and early fifth centuries, buried near the village of Holzthum.

Experts are surprised at how much of the basilica, or town hall, survived. The ancient building was part of Roman London’s political and commercial center.

The 2,000-year-old basilica was “once the beating heart of Roman London,” the Museum of London Archaeology said.

The remarkably well-preserved basilica was part of a public meeting place where citizens and politicians could socialize, shop and hear speeches in the growing city