The Roman galleries, located under Rua da Prata and Rua da Conceição, in the heart of downtown Lisbon, will then reopen to the public on 18, 19, 20, and 21 April.

However, visits to the attraction in downtown Lisbon are already sold out, with tickets for all of the days selling out in "about two hours".

The galleries have been open to the public every year since 2013, but "continue to arouse interest and curiosity among visitors" who want to know about this structure that was "discovered underground in downtown Lisbon in 1771, following the 1755 earthquake".

The monument opens "at two times of the year (April and September) for just four days", since it is "necessary to maintain relative humidity and water levels inside the building, essential for preserving the structure".