Which of the following is located at the junction of the choroid and the iris?

The structure located at the junction of the choroid (vascular layer of the eye) and the iris (the colored part of the eye) is the: Ciliary body. The ciliary body is responsible for controlling the shape of the lens through the action of the ciliary muscles. This adjustment of the lens shape helps in focusing on objects at different distances.

The other three structures are not located at the junction of the choroid and the iris:

• The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. 
• The lens is located behind the iris and is suspended by the ciliary body. 
• The fovea is a small, central pit in the retina that is responsible for sharp central vision.