Room 23 don't have a mosaic floor (anymore). Under the colonnade in front of room 23 we still see the black and white mosaic with several representations: the famous lighthouse of Portus, two sailing ships and two dolphins attacking a squid.
Between the ships and the dolphins the following text can be read:
N(avicvlariis) F(eliciter)
[NAVIC]VLARL SYLLECTI[NI]
Good luck to the shipmasters of Syllectum
NB. The M of the first line is an incorrect restoration of the letter N (with the given translation). It could also be originally NE(gotiantes) meaning merchants
Sullectum was a city in Tunesia (North Africa). They probably transported oil.
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