The interior is a big marble square room, with four central columns and also a huge pool with clear and transparent water with a beautiful ancient fountain from where the aqueduct water arrives gushing on a waterfall from the mouth of a dolphin.
The dolphin was built with stone transported from the sources of the Aqueduct and descends to the tank, seven and a half meters deep, with a capacity of 5,500 m3.
The visible excrescenses and outgrows on its body were formed by more than two centuries of water flowing permanently on it.
From the tank emerge four columns supporting a roof edge vaults which, in turn, supports the magnificent panoramic terrace overlooking the city of Lisbon.

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