Provincetown Harbor is a large natural harbor located in the town of Provincetown, Massachusetts. The harbor is mostly deep and stretches roughly from northwest to southeast and from northeast to southwest – one large, deep basin with no dredged channel necessary for boats to enter and exit. A tall green buoy east of Long Point (i.e., the tip of Cape Cod) marks the entrance to Provincetown Harbor from Cape Cod Bay. Most of Cape Cod was created by the Laurentide Glacier between 18,000 and 15,000 years ago. However, the Provincetown Spit, i.e., the land surrounding Provincetown Harbor from High Head in North Truro through all of Provincetown, consists largely of marine deposits transported from farther up the shore during the last 6,000 years. A stone wall discovered in Provincetown in 1805 is thought to have been built by Viking Thorvald Eiriksson about AD 1007, when according to Norse sagas, the keel of Ericson's ship was repaired in the harbor. Bartholomew Gosnold explored the harbor in 1602, and his mate Gabriel Archer wrote: "The fifteenth day of May we had again sight of the land, which made ahead, being as we thought an island, by reason of a large sound that appeared westward between it and the main, for coming to the west end thereof, we did perceive a large opening, we called it Shoal Hope. Near this cape we came to anchor in fifteen fathoms, where we took great store of codfish, for which we altered the name, and called it Cape Cod. Here we saw sculls of herring, mackerel, and other small fish, in great abundance. This is a low sandy shoal, but without danger..." John Smith explored the harbor in 1614 and wrote: "Cape Cod... is only a headland of high hills of sand, overgrown with shrubby pines, hurts, and such trash, but an excellent harbor for all weathers. This Cape is made by the main sea on the one side, and a great bay on the other, in form of a sickle..." Provincetown Harbor was the initial anchoring place of the Pilgrims traveling on the Mayflower in 1620, before they proceeded to Plymouth, Massachusetts.