These heavy sandals are the classic Roman army boot. Numerous examples have been found at first-century sites.
The open design of caligae allowed for the free passage of air to the feet and, unlike modern military boots, was specifically designed so as to reduce the likelihood of blisters forming during forced marches, as well as other disabling foot conditions like tinea or trench foot. Socks were not normally worn with caligae, although in colder climates such as Britain, woolen socks were used.
Caligae were constructed from three leather layers of which the top formed the outer shell. They were laced up the center of the foot and onto the top of the ankle. Additionally, iron hobnails were hammered into the soles, to provide the caligae with reinforcement and traction.
How Do I Make Mine?
Instructions on how to build or buy your own pair of caligae can be found here.