Many regard Portugal as a well-kept secret, and it still is! Once you landed in Portugal, you’d realize there are a lot more secrets waiting for you to uncover.
Galerias Romanas da Rua da Prata is undoubtedly one of these many secrets!
After the devastating earthquake in Lisbon in 1755, much of the infrastructure in the city needed to be rebuilt. It was during this period when the gallery was discovered by a man called Manuel José Ribeiro as he was trying to build a new building on Rua da Prata (c. 1770).
At first many thought this was a Roman Bath; but it was later revealed that this is in fact a cryptopoticus, a kind of structure in ancient Roman architecture built to serve as basis villae – ie; to support buildings above.
For a while, the gallery was used as water reservoirs; but after the sewage system was installed, the water was contaminated and people were prohibited from drinking the water from there.
Still flooded completely throughout the year today, the Câmera Municipal drains the underground gallery twice a year to allow visitors to have a glimpse of this mysterious vault, entering through a hole on the street right next to the track of the famous Tram N°28.
Babie Rindo 
Interesting post.
I must say Lisbon’s earthquake happened in 1755 and not 1775.
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Thanks @Morbidmind. I’ve made the correction.
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