• Free first Sunday mornings: entry is free on the first Sunday of each month until 2pm, and free for kids 4 to 12 on June 1
• Royal barges in the annex: the full-size boats and seaplanes fill a separate modern pavilion, so save time and energy for it
• Playground nearby: the Jardim Vasco da Gama playground is a few minutes' walk away for a run-around afterward

Portugal's sea history, told through scale models of ships used since the 15th century, from caravels to modern warships, plus navigation instruments, maps and paintings. The museum sits in the west wing of the Jerónimos Monastery.

A modern annex holds the big pieces: full-size royal barges with carved, gilded prows, the Santa Cruz seaplane that crossed the Atlantic in the 1920s, and the navy's first aircraft, a flying boat.