Mammoth Cave is celebrating National Park Week April 21-29 by offering a week of free tours and activities.Mammoth Cave Public Information Officer Vickie Carson says Mammoth Cave wasn’t required to offer free tours during the week—unlike parks that charge admission fees. But officials decided to offer two of the park’s cave tours—the Discovery and Mammoth Passage tours—free of charge on certain days.“We wanted to go ahead and as an invitation or a welcome or as an enticement to people to come to the park and see the cave and just offer it at a rock bottom price,” she said.Park rangers will also offer special walks and other activities during the week.