In one embodiment, a body part visualization system includes a medical instrument configured to be inserted into a body part of a living subject, a display, and processing circuitry configured to compute location coordinates of the medical instrument in the body part, and render to the display a first three-dimensional (3D) representation of the body part, the first 3D representation showing an external surface of the body part with a moving window, which moves over the external surface in the first 3D representation responsively to the computed location coordinates of the medical instrument so as to provide, via the window, an internal view of the first 3D representation of the body part, the internal view including a second 3D representation of at least a part of the medical instrument at the computed location coordinates.
