Piaget Altiplano 38mm 900P
We tend to prefer thinner watches to their bulkier counterparts, but Piaget’s Altiplano 900P is in another league entirely. This marvel of watchmaking is entirely mechanical – though manually wound – and measures in at a staggering 3.65mm, shaving off roughly 10% when compared to the previous contender. To achieve this, a variety of thinning techniques were employed, including a mechanism integrated with the case, ultrathin gears, and a lowered crystal. The result is a stunning but pricy timepiece that wears extremely comfortably and slides under even the slimmest of shirts.