Make a statement with Acanthus mollis 

Acanthus mollis or bear's breeches is a very large and striking herbaceous perennial. It has huge, glossy leaves and very tall spikes of white and purple flowers in mid summer (each white flower actually has a hood like purple bract). It makes a really statuesque, architectural statement in a border.
Acanthus mollis flowers best in a sunny position but will tolerate some shade. It will grow in any reasonably fertile, well drained soil.
Bees love the flowers.
Acanthus spinosus is very similar but has even larger leaves which are more deeply cut with long spines at their tips.