The best buildings sculpted from sand require the skills of an architect-sudden structural collapse is a significant risk-and the details depicted by some well-packed granules rival the most ornate towers and palaces you'd find on terra firma. Any of the examples here could be widely regarded as significant structures-if only they hadn't washed away hours after their completion. According toSiebert's 1990 book, The Art of Sandcastling, "Seawater is an ideal bonding agent for a sand castle. As seawater in a sculpture evaporates, salt crystals remain, forming a thin crust over the entire surface. If the sculpture is sprayed from time to time, an additional buildup of salt crystals will help preserve the piece." Take his advice, and start digging before summer ebbs away.