The Entire Process
Stalagmites are the formations that "grow up" from the floor, as water droplets fall from the stalactites on the ceiling. They form much slower; they may grow up to 0.0366" (0.929 mm) per year. Sixty eight years after the allied bombing raids would give us 2.5" tall formations, which is pretty close to what we see here.
Some shards of broken soda straw stalactites can be seen along the back wall.