Clear back into the Bronze Age, in fact:
The Hellenic Ministry of Culture, Education and Religious Affairs has announced that remnants of a massive Bronze Age city have been discovered submerged in the Aegean Sea. The settlement, which dates back approximately 4,500 years, covers an area of 12 acres and consists of stone defensive structures, paved surfaces, pathways, towers, pottery, tools, and other artifacts.
Among the tools are obsidian blades dating back to around 3200 B.C. It's among the oldest of cities discovered to date; some 6,000 artifacts have thus far been recovered. The city was built at about the same time as the pyramids in Egypt. It's presently unclear as to whether the city was submerged by earthquake, subsidence, or rising sea levels.
In any case, there are a number of submerged cities around the planet.