Giant reed - Arundo donax variegata - can apparently grow up to 7 metres high. After planting ours two years ago, it is now perhaps 2 metres high. And spreading fast!
It is a dramatic, often variegated grass with the leaves on strong thick stems, which grow from hard, dense rhizomes.
Although often found in damp soil conditions note that it does NOT only grow in wet conditions - but it will grow faster and more enthusiastically in proximity to water.
Care is required due to the enthusiasm with which giant reed grows - in many places Giant Reed is considered to be a weed or pest plant, difficult to control or destroy, blocking waterways, casting shade all around, and displacing nearby plants.
So I would recommend one as a feature plant, but not near a waterway and not where it can not be controlled.
