What is the Esna Lock in the Nile River between Luxor and Aswan?

Answers:

• The Lock of Esna (or Esna arches) is an engineering building that works as a "water elevator" for ships. Because there is a difference in the water level in the Nile before and after the barrage, it is located 160 km north of Aswan and 60 km south of Luxor.
  – Nile Cruise Guide