(Slide Show) At the eminent Belgian landscape-design firm Wirtz International, shapes are as important as plants. Hedges are shorn into curving coils that wander dreamily across pristine lawns, while shrubs are trimmed into cloudlike formations that seem to billow. Artificial hills are carefully graded, their gentle swellings adding movement to parks and gardens. The effects are both stately and slightly surreal. Take a walk through some of the greatest work in the firm’s six-decade-plus history in AD’s exclusive slide show.