A sandcastle is a structure built from wet sand, usually at the beach. When you mix sand with just the right amount of water, it becomes moldable and sticky enough to shape into towers, walls, and other architectural features. Building sandcastles is a classic beach activity where people use buckets, shovels, and their hands to create everything from simple mounds to elaborate fortresses complete with moats, turrets, and drawbridges.

Sandcastles use sand that's damp but not too wet or too dry. Builders often work in teams, with some people gathering and wetting sand while others shape and carve details. Skilled sandcastle artists can create incredibly detailed sculptures, from realistic castles to dragons, mermaids, or even replicas of famous buildings.

Sandcastles are temporary by nature. Waves wash them away, or they dry out and crumble. People sometimes use the phrase building sandcastles to describe making plans or dreams that won't last. Building sandcastles can also involve engineering, patience, and enjoying the process of creation.