Stay in my tour boat in the marina at Belém. It's a unique way to visit Lisbon, surrounded by the water and the loveliest sights Lisbon has to offer.
Bering is available for a single night (great for special occasions) or longer. The boat is used for tours during the day, so you'd have to be away from 11:00 to 19:00 on most days.
This is a quirky little listing for the right kind of traveller. Includes heavily discounted wine and cheese tours of Lisbon from the river :)