Jerusalem (CNN) -- Israeli archaeologists have discovered an ancient Roman bathhouse that was probably used by the soldiers who destroyed the Second Temple in Jerusalem, the Israel Antiquities Authority announced Monday.

The surprise discovery includes the mark of Rome's Tenth Legion -- as well as the paw print of a dog.

The animal probably belonged to one of the soldiers, excavation director Ofer Sion said.

The print "could have happened accidentally or have been intended as a joke," he said.

Archaeologists were not expecting to find the Roman structure in the Jewish Quarter, where a mikvah, or Jewish ritual bath, was being constructed.

"The mark of the soldiers of the Tenth Legion, in the form of the stamped impressions on the roof tiles and the in situ mud bricks, bears witness to the fact that they were the builders of the structure," he said.

"It seems that the bathhouse was used by these soldiers who were garrisoned there after suppressing the Bar Kokhba uprising in 135 CE (A.D.), when the pagan city Aelia Capitolina was established," he explained.

The structure includes a number of plastered bathtubs in the side of a pool, a pipe used to fill it with water, and a white industrial mosaic pavement on the floor.

Hundreds of terra cotta roof tiles were found on the floors of the pool, indicating it was a covered structure, he added.

The bathhouse tiles are stamped with the symbols of the Tenth Legion "Fretensis" -- LEG X FR, he said.

The discovery shows that the Roman encampment established to help keep Israel under Roman domination was larger than previously thought, another expert said.

"Despite the very extensive archaeological excavations that were carried out in the Jewish Quarter, so far not even one building has been discovered there that belonged to the Roman legion," Jerusalem district archaeologist Yuval Baruch said.

"The absence of such a find led to the conclusion that Aelia Capitolina, the Roman city which was established after the destruction of Jerusalem, was small and limited in area," he said.

But the discovery of the 1,800-year-old bathhouse "together with other discoveries of recent years, shows that the city was considerably larger than what we previously estimated," he said.

Understanding the ancient Roman city of Aelia Capitolina is "extremely valuable," he said, because it determined the shape of Jerusalem's historic walls "and the location of the gates to this very day."