The Decagonal Prism
The decagonal prism is a 3D uniform polyhedron bounded by 2 decagonal faces and 10 squares. It has 30 edges and 20 vertices. It may be considered to be the extrusion of the decagon.
A decagonal prism can be attached to a pentagonal cupola (J5) to form an elongated pentagonal cupola (J20), or to a pentagonal rotunda (J6) to form an elongated pentagonal rotunda (J21).
Projections
In order to be able to identify the decagonal prism in various projections of 4D objects, it is useful to know how it appears from various viewpoints. The following are some of the commonlyencountered views:
Projection  Envelope  Description 

Regular decagon  Decagoncentered parallel projection. 

Rectangle  Parallel projection centered on a vertical edge. 

Rectangle  Squarecentered parallel projection. 

Decagon  Vertexcentered parallel projection. 
Coordinates
The Cartesian coordinates of the decagonal prism, centered on the origin and having edge length 2, are all changes of sign of:
 (2φ, 0, 1)
 (1, √(3+4φ), 1)
 (φ^{2}, √(2+φ), 1)
where φ=(1+√5)/2 is the Golden Ratio.
Occurrences
The decagonal prism occurs in the following uniform polychora: