Travertine naturally has "holes" caused by decaying plant life bubbling up through the stone as it was being formed 20 million years ago. Sometimes these holes are filled at the factory, and sometimes not. Left unfilled, they create the perfect spot for dirt to collect and ruin the look of the floor. Here in Southern Utah, we have an abundance of this flooring and cleaning it properly is one of our specialties. This travertine floor responded well to our process and looks like new again.