As part of our wedding arrangements in Rome, we were looking for a place to house 11 people, in a central location to provide everyone easy access to the major sights. For a large group, there weren't many options. However, we came across this apartment and it fit our needs perfectly.

The apartment is in an excellent location, situated right in between Piazza Navona and Campo dei Fiori - which our guests ventured to every night to grab drinks/dinner and people watch. The Colloseum and Vatican are a bit further away, but easy enough to take the bus to. All of our guests (including those that stayed in other areas of Rome) all agreed that the location could not be beat.

The apartment itself was very spacious, with enough variety in bed sizes to accommodate our mixed group of couples and singles (we required 3 double and 5 single beds). There seemed to be an extra cot and a sofa bed - so this place can definitely house at least 13 people (if not more).
The wifi was decent, however we did notice that if all of us got on it at the same time, the router would need to be restarted. Also, the router is located right next to the front door, which is one side of the apartment, so the two rooms on the other end did not get very much wifi reception.
The bedrooms were spacious, with tall ceilings and large windows that provided a nice breeze. Though the apartment does not have air conditioning, the breeze was more than enough to cool the apartment - during our stay the temps were in the low 80s, and the apartment was just fine due to the breeze.

The apartment has a total of 4 full bathrooms - two bathrooms in the hallway, one of the rooms on the end of the apartment has its own bathroom, and another bathroom at the end of the hallway next to the last room. Washer/Dryer is located in back of one of the bathrooms.

The apartment is handled by a private company. They also provide taxi booking from the airport to the apartment/vice versa, which we used without any issue. They also helped us book a private chef for a welcome dinner at very low cost - the food was excellent! At check in, Silvano met us at the apartment and was very thorough in walking us through the apartment. Daniela was also very responsive via email during our stay. Very good service - no complaints! Our florist for the wedding (Dordas flowers), who happened to have his shop across the street, even inquired about the apartment for any future weddings he might do.

Extras -
There are three small supermarkets near the apartment.
In case you need a taxi, there is also a taxi stand right across the street.
Grom in Campo Dei Fiori is an excellent gelateria
Baffeto 2 - excellent pizza
Osteria da Fortunata - Excellent Ox Tail pasta