An old mill is a type of amusement park ride with unaccompanied boats floated on guideways through dark tunnels. These themed dark rides are known by a variety of names, including tunnel of love and river cave. While generally considered a gentle ride, a variation that ends with a climactic splashdown, similar to the modern-day log flume, is known as a mill chute.

In its earliest incarnations, riders were taken by two-passenger boats through dark passages. There were two major themes: a relaxing romantic ride encouraging the couple to cuddle, or a spooky horror ride encouraging the couple to cling to one another. The darkness provided a degree of privacy and the frightening scenes offered a socially acceptable excuse for the physical contact at a time when public affection or even holding hands was considered inappropriate. The boats, hearts and many other themes seem to be based around the appearance of Luvdisc.