It was Peter the Great himself who conceived its general scheme. His first surviving sketches of the future Peterhof structures show that the Tsar was familiar with their European prototypes. Peter the Great offered to erect on the slope of the terrace two grottos and two cascade stairways to let water run down to a rectangular pool connected by a canal with the sea. The construction of the canal began in 1715 and of the Lower Grotto in May 1716.