“The Silver Aqueduct had its opening on March 28th, 1537, and is considered one of the most important works of the city during the first half of the XVI century. Its construction took six years, under supervision of the royal architect Francisco de Arruda, and it stretches for about 18 kms, up to the Divor estate, where its water supply lies.  
(…) In the Geraldo Square, where the aqueduct ended, stood a fountain “ornate by marble lions” connected to a roman arch, both destroyed during the renovation of the main square of the city, and replaced by the present Geraldo fountain.  
Along the centuries the Silver Aqueduct underwent several changes, from additions to demolitions. The most visible ones were the various fountains and springs along the city course.” 

Source: Site DGPC – Direção Geral do Património Cultural 
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GPS: 38°35'19.9"N | 7°54'58.4"W