Domus and Insula
Domus or Roman house was coordinated around colonnaded courts with open front doors enabling a look to the interior atrium. These courtyard houses were surrounded with peristyle columns which hold dining rooms, baths and kitchens. Especially the Pompeian houese were decorated. One could see paintings on the walls showing narrative scenes. The villa type emerged from the luxurious life on the countryside consisting of a larger scale with more openness for the landscape vistas. The multilevel apartment, insula, evolved after the Great Fire; they have built these blocks fireproof using brick-faced concrete on wide streets.
The Grand Projects of Trajan and Hadrian
Trajan’s Forum was a four level market comlex which was three times of Julius’s Forum had vaulted structures serving as the retaining walls. The forum had two libraries, a basilica, a temple. Like in the Greek stoa,the interior was highly transparent due to its raised Corithian columns without the bearing walls.
Hadrian took the Roman vaulted style to another level. The temple of Pantheon which was part temple part throne room provided a hemisperical space contributed to concrete technology. The dome with an oculus on the top acted with the similar task as a keystone by behavng like a compression ring to lock the structure. It was also the source of the light.