Around 1350, in Padua, Giovanni de’ Dondi built an astrarium that described the celestial movements of the sun, the moon, and the five known planets. It was, in addition to being a perpetual calendar, a clock. “So great is the marvel,” wrote a witness, “that great astronomers come from distant places to admire his work.” Versions of the astrarium moved from the castle to the square and then, after World War I, to the wrists of everybody. Most recently, the cell phone seemed to make horological armwear moot, but now Apple Watch, seen here with a leather strap and stainless-steel casing, and available early 2015, can do all de’ Dondi’s clock did. Plus it monitors your pulse and, if you like, shares it with Apple Watch–wearing friends.

A tiny marvel.