There are three fantastic sights in this area - Torre de Belem, Monument to the Discoveries and for me the best was Mosteiro dos Jeronimos.
Get the 15 tram from Praca de Figueira and get off after Mosteiro dos Jeronimos. You need to walk up aways and take the footbridge over the road to get to the Torre de Belem, and the Monument to the Discoveries.
Updates
Send your feedback or queries to been.there@guardian.co.uk
Search Been there
If you consider the ticket taker & statues as the first room, then as you enter the 2nd room, look to your right for WC & stairs to 2nd floor. On 2nd floor & explore all of it, then do all of the huge ground floor & other building with several royal barges.