Plaza de Armas, Central Lima. This is the spot where Francisco Pizarro founded the city in 1535. The north side is dominated by the Government Palace (rebuilt in 1937), home of Peru's president. You can watch the changing of the guard here at 11:45 each morning.
On the east side of the Plaza you'll find the Cathedral. Construction of this church began in 1564 and was completed in 1622. Unfortunately is was reduced to rubble in 1746 by an earthquake and was subsequently rebuilt and completed by 1755. The supposed remains of Francisco Pizarro lie in a small chapel, the first on the right of the entrance, in a glass coffin.
Open Tues-Sun 10:00 - 18:00, Entrance fee of US$2 includes entrance to the Religious Art Museum inside.