Having crossed the area of the former street – cardo – one sees the archaeological remnants of the 4th and 5th century basilicas. To the left are the remnants of a large city gate built in the Roman period, which led to the northern port of ancient Parentium. The gate was walled in during the Middle Ages when the area on inner side was filled in and turned into a cemetery. Large areas of the floor mosaic that are visible are not original, but copies made in the first half of the 20th century to replace the original mosaic floors of the oldest church. The original fragments are those exhibited on the ground floor of the Episcopal Palace. The reason why they had to be replaced is that they are located at the level, which was meanwhile, 1600 years after their creation, reached by the sea. The sea level on the northern Adriatic coast rises unstoppably at a rate of approximately 1 mm per year. Therefore, when the tide is at its highest, these mosaics are more than 20 cm below the sea level. The archaeological remnants speak of two churches which had been erected before the Euphrasian Basilica – the 4th century one called by the scientists the First Basilica and the 5th century Pre-Euphrasiana. The First Basilica was a three-nave structure partly erected on the remnants of secular Roman structures. It was turned into dual Pre-Euphrasiana consisting of two three-nave churches. The larger Pre-Euphrasian basilica is located underneath the current Euphrasian Basilica, and the fragments of its floor mosaic can be seen inside the currently existing cathedral.