Two houses from the time of Melchizedek have been excavated in the City of David that was then known as Salem. These houses were dated to about 2700 B.C. and were destroyed by the Canaanite city wall in 1850 B.C. These type of long-houses (with a single door in the long side of the house) are known from other excavations.
No city wall from the time of Melchizedek has been found, perhaps confirming that he was King of Peace indeed, as mentioned in Hebrews 7.2.