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).
Attaching two cupolae to a decagonal prism produces the elongated pentagonal orthobicupola (J38) or the elongated pentagonal gyrobicupola (J39), depending on the orientation of the two cupolae relative to each other.
Replacing one of the cupolae with a pentagonal rotunda instead produces the elongated pentagonal orthocupolarotunda (J40) or the elongated pentagonal gyrocupolarotunda (J41), respectively.
Attaching two pentagonal rotunda to a decagonal prism produces the elongated pentagonal orthobirotunda (J42) or the elongated pentagonal gyrobirotunda (J43), depending on the orientation of the rotundae with respect to each other.
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: