Wonderful city. Museums, caipairnho Fado. Say 'Obrigado/a' (thank you) to everyone. The tiny streetcars up to the castle/fortress. Rent a car and drive to the Algarve for some sun/sand and cataplana (seafood stew). Or go up to Porto for some, well, port. Enjoy the Vinho Verde, (white) or Roja (red) all over for cheaper than water.
You'll want to go back! We do.
Jim