Radiation heat transfer moves at the speed of light, because it is a type of light! These light waves are categorized in the part of the light spectrum called Infrared.
You can feel radiative heat from:
Any surface that has any heat at all
The surface of the sun through the window to the floor
The sun to the roof, the roof to the ceiling
Radiation heat gain and loss happens primarily through windows...
You can see radiation using a FLIR camera - Focused Laser Infrared - which shows a thermographic reading of the hot and cold things in a space. The picture below shows a kitchen: