Lisbon's main boulevard, the Avenida da Liberdade, starts at an oval shaped square known as the Praça dos Restauradores. At its center stands a large obelisk, the Monumentos dos Restauradores.The obelisk was erected here in 1886 and commemorates the restoration of Portuguese Independence from Spain in 1640. Portugal had been under Spanish administration for sixty years when the Portuguese nobility started a revolt on December 1, 1640. The revolt triggered the Restoration War - a twenty-eight year war between Spain and Portugal - that ended with the Treaty of Lisbon, in which Spain recognized the sovereignty of Portugal.