The map, a beautiful birds-eye-view of Jerusalem, shows in detail the walls, the gates, the main streets and the churches of the city. The main thoroughfare, the Cardo maximus (Cardo, in short) was a colonnaded street bisecting the city from north to south, from todays Damascus Gate to the Zion Gate. Along the Cardo in the map, two large church complexes are clearly shown the Holy Sepulcher in the north and the Nea Church at the southern end. 
The Madaba Map, the earliest graphic representation of Jerusalem, guided archaeologists in their search for the remains of Byzantine Jerusalem. After the reunification of Jerusalem in 1967, excavations were conducted in the Jewish Quarter (located in the southeastern part of the Old City). The Nea Church and the Cardo were discovered, in the locations depicted in the Madaba map. 
The Nea Church 
In Jerusalem he (Justinian) built a church in honor of the Virgin which is beyond compare. People call this church the New Church (Nea). Thus wrote Propitious, court historian of the emperor Justinian. The full name of the edifice was the Church of Mary, Mother of God. Propitious recounts details of its construction and the names of the various buildings which made up the large church complex. 
Portions of the church were uncovered on the southern slope of the Jewish Quarter of the Old City. The church was built on a massive podium supported by thick walls of stone and concrete resting on deep bedrock. It was a very large structure, 115 m. long and 57 m. wide, divided by four rows of columns which supported the roof. The eastern wall was especially broad (6.5 meters) and contained side apses, 5 meters in diameter. Marble pavement covered the floor. 
Along the southern side of the church, where the bedrock is at great depth, a very large subterranean water reservoir was found, completely preserved. Some of the annexes of the church had been built above it. The reservoir measures 33 x 17 m. and is divided into vaults supported by arches which rest on huge (5 x 3.5 m.) piers, ten meters high. The interior of the reservoir was coated with a thick layer of hard plaster; it had a capacity of thousands of gallons of water.
A surprising discovery was a dedicatory inscription placed in the water reservoir. Found high on the southern wall, the Greek inscription, in red-painted plaster relief letters, reads: 
And this is the work which our most pious Emperor Flavius Justinian carried out with munificence, under the care and devotion of the most holy Constantine, priest and Hegumen, in the 13th (year of the) indiction.*
(Probably the year 549-550) 
The inscription provides evidence for the identification of the remains with the Nea Church, its location corroborated by the Madaba Map.
The Cardo 
The remains of an elaborate north-south colonnaded street the Cardo were found in the center of the Jewish Quarter, exactly as depicted in the Madaba map. A 200-meter-long section of the street, four meters below present-day street level, was exposed. Its northern part was laid upon several meters of earth fill, whilst the southern end was on leveled bedrock, which created a six-meter-high rock scarp on its western side. 
The Cardo was 22.5 m. wide, divided by two rows of stone columns into a broad street flanked on either side by five-meter-wide covered passageways. A wooden beam construction supported the roofing, probably of ceramic tiles. Bordering the street on its eastern side was an arcade of large arches supported by piers built of ashlars. Shops lined the street along its southwestern part; more shops were located behind the arcade of arches. 
The monolithic columns, of hard limestone, were found in fragments, incorporated into later structures. The bases are in Attic profile, while the capitals are carved in the Corinthian style. The columns, five meters high, have been reconstructed in their original positions in the Cardo. The well-hewn paving stones, laid in parallel rows, are smoothed and cracked with age. 
The southern part of the Cardo, uncovered in the Jewish Quarter, was built during the reign of the emperor Justinian (527-565), as a continuation of the earlier, Roman, northern part, thus linking the two main churches of Byzantine Jerusalem the Holy Sepulcher and the Nea Church. 
Along the reconstructed part of the Cardo one can walk today, as did people some 1500 years ago. In the twelfth century, the Crusaders built a covered bazaar over a section of the Cardo; from this section, the debris of centuries have been removed and modern stores offer their wares to shoppers. 
The remains of the Nea Church and of the Cardo were un-covered by N. Avigad on behalf of the Hebrew University of Jerusalem
Source: Israeli Foreign Ministry