An urban archaeologist working anywhere in the world can imagine this scenario: armed with a small digging tool and a soft brush, the archaeologist stands at a freshly cut trench facing off a construction crew driving bulldozers. At stake is the past--the discovery and preservation of our history. Across the gap is the future--progress and new buildings for a modern world. A battle ensues. It happened in Dublin in the early 1960s.

While investigating and salvage-excavating the site for a new municipal office complex, archaeologists made one of the most important and exciting...