In the time of Peter the Great, the sea floor just north of the Petergof site and to the east toward St. Petersburg was too shallow for either commercial ships or warships. However, to the west of Petergof, the sea floor dropped off to be deep enough for sea vessels. Accordingly, when Peter the Great decided to build St. Petersburg at the eastern end of the Gulf of Finland, he first captured the Kotlin Island clearly visible from the Petergof site just to the northeast in the middle of the Gulf. At Kotlin Island he would build the commercial harbor for St. Petersburg as well as the Kronshtadt fortifications across the 20 kilometers (12 mi) of shallow sea to provision and defend the Navy that he would build.
Peter the Great first mentions the Petergof site in his journal in 1705, during the Great Northern War, as a good place to construct a landing for use in traveling to and from the island fortress of Kronshtadt. In 1714, Peter began construction of the Monplaisir ("my pleasure") Palace based on his own sketches of the palace that he wanted close to the shoreline. This was Peter's Summer Palace that he would use on his way coming and going from Europe through the harbor at Kronshtadt. On the walls of this seacoast palace hung hundreds of paintings that Peter brought from Europe and allowed to weather Russian winters without heat together with the dampness of being so close to the sea. And in the seaward corner of his Monplaisir Palace, Peter made his Maritime Study from which he could see Kronshtadt Island to the left and St. Petersburg to the right. Later, he expanded his plans to include a vaster royal château of palaces and gardens further inland, on the model of Versailles. Each of the Tsars after Peter expanded on the inland palaces and gardens of Peterhof, but the major contributions by Peter the Great were completed by 1725. Peter had also entertained plans of a similar palace atStrelna, a short way to the east, but these plans were abandoned