House Mercator
You can go her if you are Titus, staying with Titus, or visiting. House Mercator has made it clear they do not wish to be swept up in creepy political things involving undermining Visigoths. They've stepped back from directly being involved in anything but their own affairs, though they are willing to arrange and support from the sidelines.
That being said, they wouldn't mind if Titus had a few guests here, as long as they didn't leave any trails that could be traced back to House Mercator.
House Mercator has a villa in the wealthy Carinade district, on the extreme southwest of the city. This neighborhood is actually outside the walls, on the rugged hill overlooking the ocean, west of the Pharo. Because of its beautiful views, and remoteness yet accessibility from the bustle of the city, it became the most popular neighborhood for the richest families in Massilia. The Mercator property overlooks the sea, and is built around a wide terrace with a pool.
Not many Mercators actually live here. They have their property here mostly for business purposes, and as a result it has lots of room. Currently it is home to Filana Mercator, who was married to a cousin of Titus before his untimely disappearance at sea. Their son, Milo Mercator, is only eighteen but a math and business prodigy, and manages everything they Mercators do here singlehandedly, at least from the administrative point of view- they have dozens of servants and workers, and a warehouse and dock in the New Docks district.
Despite his young age Milo is the "business geek" of Massilia. He frequents the markets and docks, learning who is trading what, who is looking for what, and what prices are like.
If he took time away from business, he could be the Wall Street Journal of Massilia.