The mighty slate rock Lorelei in the Romantic Rhine Valley - around 16 miles/ 25 km from Rudesheim and 50 miles/80 km from Frankfurt airport - rises up almost vertically to 145 yards/132m above the water-level. Downstream the river is squeezed into its narrowest and deepest (24 yards/22m) point, so the Middle Rhine at this point used to be very difficult to navigate and the correct passage is (today) clearly marked with buoys. Even in the 19th century, reefs and rapids made it extremely dangerous for ships to pass this point. The legend tells us, that a siren called "Lorelei" bewitched the hearts of the sailors and when they looked up to the rock, their boat crashed and they sank.