Here's some more from Plato about foreign travel into and out of a good city, this time the Laws' Magnesia. (This is Jowett's translation of Laws 12 950b-953e):
And our Cretan colony ought also to acquire the fairest and noblest reputation for virtue from other men; and there is every reason to expect that, if the reality answers to the idea, she will before of the few well-ordered cities which the sun and the other Gods behold. Wherefore, in the matter of journeys to other countries and the reception of strangers, we enact as follows:-
In the first place, let no one be allowed to go anywhere at all into a foreign country who is less than forty years of age; and no one shall go in a private capacity, but only in some public one, as a herald, or on an embassy; or on a sacred mission. Going abroad on an expedition or in war, not to be included among travels of the class authorized by the state. To Apollo at Delphi and to Zeus at Olympia and to Nemea and to the Isthmus,-citizens should be sent to take part in the sacrifices and games there dedicated to the Gods; and they should send as many as possible, and the best and fairest that can be found, and they will make the city renowned at holy meetings in time of peace, procuring a glory which shall be the converse of that which is gained in war; and when they come home they shall teach the young that the institutions of other states are inferior to their own. And they shall send spectators of another sort, if they have the consent of the guardians, being such citizens as desire to look a little more at leisure at the doings of other men; and these no law shall hinder. For a city which has no experience of good and bad men or intercourse with them, can never be thoroughly, and perfectly civilized, nor, again, can the citizens of a city properly observe the laws by habit only, and without an intelligent understanding of them. And there always are in the world a few inspired men whose acquaintance is beyond price, and who spring up quite as much in ill-ordered as in well-ordered cities.
These are they whom the citizens of a well ordered city should be ever seeking out, going forth over sea and over land to find him who is incorruptible-that he may establish more firmly institutions in his own state which are good already; and amend what is deficient; for without this examination and enquiry a city will never continue perfect any more than if the examination is ill-conducted.
Cleinias. How can we have an examination and also a good one?
Athenian Stranger. In this way: In the first place, our spectator shall be of not less than fifty years of age; he must be a man of reputation, especially in war, if he is to exhibit to other cities a model of the guardians of the law, but when he is more than sixty years of age he shall no longer continue in his office of spectator, And when he has carried on his inspection during as many out of the ten years of his office as he pleases, on his return home let him go to the assembly of those who review the laws. This shall be a mixed body of young and old men, who shall be required to meet daily between the hour of dawn and the rising of the sun. They shall consist, in the first place, of the priests who have obtained the rewards of virtue; and in the second place, of guardians of the law, the ten eldest being chosen; the general superintendent of education shall also be member, as well the last appointed as those who have been released from the office; and each of them shall take with him as his companion young man, whomsoever he chooses, between the ages of thirty and forty. These shall be always holding conversation and discourse about the laws of their own city or about any specially good ones which they may hear to be existing elsewhere; also about kinds of knowledge which may appear to be of use and will throw light upon the examination, or of which the want will make the subject of laws dark and uncertain to them. Any knowledge of this sort which the elders approve, the younger men shall learn with all diligence; and if any one of those who have been invited appear to be unworthy, the whole assembly shall blame him who invited him. The rest of the city shall watch over those among the young men who distinguish themselves, having an eye upon them, and especially honouring them if they succeed, but dishonouring them above the rest if they turn out to be inferior.
This is the assembly to which he who has visited the institutions of other men, on his return home shall straightway go, and if he have discovered any one who has anything to say about the enactment of laws or education or nurture, or if he have himself made any observations, let him communicate his discoveries to the whole assembly. And if he be seen to have come home neither better nor worse, let him be praised at any rate for his enthusiasm; and if he be much better, let him be praised so much the more; and not only while he lives but after his death let the assembly honour him with fitting honours. But if on his return home he appear to have been corrupted, pretending to be wise when he is not, let him hold no communication with any one, whether young or old; and if he will hearken to the rulers, then he shall be permitted to live as a private individual; but if he will not, let him die, if he be convicted in a court of law of interfering about education and the laws, And if he deserve to be indicted, and none of the magistrates indict him, let that be counted as a disgrace to them when the rewards of virtue are decided. Let such be the character of the person who goes abroad, and let him go abroad under these conditions.
In the next place, the stranger who comes from abroad should be received in a friendly spirit. Now there are four kinds of strangers, of whom we must make some mention-the first is he who comes and stays throughout the summer; this class are like birds of passage, taking wing in pursuit of commerce, and flying over the sea to other cities, while the season lasts; he shall be received in market-places and harbours and public buildings, near the city but outside, by those magistrates who are appointed to superintend these matters; and they shall take care that a stranger, whoever he be, duly receives justice; but he shall not be allowed to make any innovation. They shall hold the intercourse with him which is necessary, and this shall be as little as possible.
The second kind is just a spectator who comes to see with his eyes and hear with his ears the festivals of the Muses; such ought to have entertainment provided them at the temples by hospitable persons, and the priests and ministers of the temples should see and attend to them. But they should not remain more than a reasonable time; let them see and hear that for the sake of which they came, and then go away, neither having suffered nor done any harm. The priests shall be their judges, if any of them receive or do any wrong up to the sum of fifty drachmae, but if any greater charge be brought, in such cases the suit shall come before the wardens of the agora.
The third kind of stranger is he who comes on some public business from another land, and is to be received with public honours. He is to be received only by the generals and commanders of horse and foot, and the host by whom he is entertained, in conjunction with the Prytanes, shall have the sole charge of what concerns him.
There is a fourth class of persons answering to our spectators, who come from another land to look at ours. In the first place, such visits will be rare, and the visitor should be at least fifty years of age; he may possibly be wanting to see something that is rich and rare in other states, or himself to show something in like manner to another city. Let such an one, then, go unbidden to the doors of the wise and rich, being one of them himself: let him go, for example, to the house of the superintendent of education, confident that he is a fitting guest of such a host, or let him go to the house of some of those who have gained the prize of virtue and hold discourse with them, both learning from them, and also teaching them; and when he has seen and heard all, he shall depart, as a friend taking leave of friends, and be honoured by them with gifts and suitable tributes of respect.
These are the customs, according to which our city should receive all strangers of either sex who come from other countries, and should send forth her own citizens, showing respect to Zeus, the God of hospitality, not forbidding strangers at meals and sacrifices, as is the manner which prevails among the children of the Nile, nor driving them away by savage proclamations.