Source of ancient historyWatch
Herodotus was probably the first 'historian' (the issues around his style of recording things notwithstanding). Much information is gleaned from writings of contemporaries that were not actual historians, but were just discussing in letters the socio-political and cultural discoveries and occurrences of the time. Such people pop up in every era of history.
One example of contemporary Roman writings would be the Vindolanda tablets:
Sometimes these sorts of precious historical artifacts are open for display to the general public. For example, Salisbury Cathedral has a Medieval copy of the Magna Carta on display:
And the great museum in Naples has some of the Roman scrolls from the Villa of the Papyri on display:
But more often than not, these sorts of precious original writings are usually kept in safe & secure temperature controlled storage units where they are only accessible to a select few.
Sometimes new ancient writings discoveries turn up in surprising places, such as inside of book bindings:
And one of the most famous ancient writing discoveries is of course the Dead Sea Scrolls:
In terms of who owns the Dead Sea Scrolls, lots of countries are trying to lay a claim to them:
You can tell by items left behind, pottery, poetry, ledgers, coins, all these attest to a high level of civility.