"Gullfoss is one of the most popular tourist attractions in the country. The wide Hvítá rushes southward. About a kilometre above the falls it turns sharply to the right and flows down into a wide curved three-step "staircase" and then abruptly plunges in two stages (11 m and 21 m) into a crevice 32 m (105 ft) deep. The crevice, about 20 m (60 ft) wide, and 2.5 km in length, extends perpendicular to the flow of the river. The average amount of water running over this waterfall is 140 m³/s in the summertime and 80 m³/s in the wintertime. The highest flood measured was 2000 m³/s.

"As one first approaches the falls, the crevice is obscured from view, so that it appears that a mighty river simply vanishes into the earth." (Wikipedia)