Quatermass And The Pit (1967)

While digging a new Underground line in London, a construction crew discovers first: a skeleton, then what they think is an old World War II German missile. Upon closer examination the "missile" appears to be not of this earth. This movie examines the age old question of how we came to be on this planet. It is surprisingly scary.

IMDb: https://www.imdb.com/title/tt0062168