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Professional sand sculptors can connect towers quite far apart, just inserting a bridge of sand between them and smoothing it out.[11] This is pretty difficult, but if you're up for a challenge, use the same approach recommended earlier for the base of your castle: slightly wet sand, very densely packed.

The easiest way to build an arch is to build two towers quite close together, leaning slightly inward as they go higher. As soon as the towers are close enough together, make a bridge between the tower tops with your hand. Pile more wet sand over your hand to connect the two towers, and wait a few seconds for it to dry. Heavy arches are more likely to collapse, so scrape off as much sand as you can from the sides and top before you move your hand away.