A lighting arrangement for illuminating a passage, such as a wind tower or tunnel, includes at least one lighting unit having a generally rectangular base with bottom, side and end walls cooperating to define an open-topped chamber, a pair of light energy sources arranged partially in the housing chamber for directing light beams toward opposite ends of the housing, respectively, and a cover member formed of light-transmitting material, which cover member is connected with the base to extend over the light energy sources and to close the housing chamber. The cover member includes a concave dome portion containing a cavity within which the light sources are mounted. Opposite areas of the cover dome portion define collimating devices for concentrating the light beams in opposite directions longitudinally of the passage that is to be illuminated. A plurality of lighting units are longitudinally-arranged in the passage, and are electrically connected in series.