The Alpine mountain belt was formed by the collision of the Eurasian and African plates in the geological past, during which parts of the colliding plates sank into the earth's mantle. Using seismological data from distant earthquakes recorded by the AlpArray Seismic Network, we have derived an image of the current location of these subducted parts in the earth's mantle. Their quantity and spatial distribution is key information needed to understand how the Alpine orogen was formed.