This is an impressive Roman monument that will leave you amazed. It is near the Cathedral and admission is free. It was Constantine's throne room and is the largest individual space that has survived since that time. The outside has been excellently preserved so that it´s not the typical building in ruins but a proper Roman structure as it was 2000 years ago. The inside is even more surprising because of the architectural features. The Romans, to give it even more of a sense of grandeur, made the windows near the door smaller which gives the sensation that you´re entering the Basilica at an even greater depth.