At the mouth of the Tagus river and guarding the entrance to the city of Lisbon is Torre de Belem or Belem Tower. The Tower was built as a fortress in the middle of the Tagus in 1515-21 and is of significant historical importance. It was from here that the caravels set out to discover Portugal's trade routes. Another of Lisbon's iconic attraction along the waterfront is the Monument to the Discoveries. A more recent addition is the Monument to the Overseas Combatants. The photos in this gallery were taken over different visits to Lisbon. Read more about Belem Tower HERE. Read about the Monument to the Overseas Combatants HERE. Read about the Mariner's Compass HERE. Read about the Monument to the Discoveries HERE.