The town of Helsingor on the East coast of Denmark attracts thousands of visitors every year. Their destination is Kronberg Castle, or "Hamlet's Castle" as it has come to be known.
The castle was built by King Eric VII in the early fifteenth century. Its purpose was to command the narrow channel of water navigated by merchant ships on the Baltic trade routes. Each and every ship passing through the sound had to heave to at Helsingor and a tax of one English noble was levied on it.
Any ship that did not stop would be fired on by the cannon on the ramparts of the castle.
Far more often, though, the cannon were fired in celebration rather than in anger. The Danish court was noted for its drinking bouts and on ceremonial occasions, whenever the King or one of his courtiers proposed a toast, the kettle drummers and trumpeters would proclaim it and the gunners on the castle tower would pick up the signal and fire the great cannon on the castle tower.
The custom of "cannon healths" is referred to three times in Hamlet, twice by Claudius in Act One Scene Two, and in Act Five Scene Two, and once by Hamlet in Act One Scene Four.
In that scene, Horatio asks Hamlet why there was a sudden flourish of trumpets and firing of ordinance. Hamlet tells Horatio that it happens whenever the king stands up and drinks down a draught of "Rhenish".
One reason, of course, is that it fits the line, but another is that German Rhine wine was the wine of choice at the time, and Yorick reportedly poured a whole flagon of the stuff on the Gravedigger's head.
Authentic details such as those cause some people to speculate that Shakespeare had actually been to Denmark and visited Helsingor during his "lost years", just as others suppose that he must have been to Italy because of the accurate representation of small details in Italian plays such as The Taming of the Shrew, or Romeo and Juliet.
Furthermore, in the mid 1580s, a group of English actors went to Denmark and performed at Helsingor. Three of the five actors who are recording as having gone to Denmark are also among "The Names of the Principall Actors" listed in the first Folio edition of Shakespeare's plays, published in 1623.
That Shakespeare is not named as one of the players who went to Denmark is no proof that he did not go. Since every play required more than five actors it is not unreasonable to suppose that Shakespeare was one of them.
But nor is the accuracy of some of the details proof that Shakespeare went to Denmark. Other details are in the play that are accurate but from a time before Shakespeare could have been in Denmark, while other details are not accurate.
In short, there is no conclusive evidence to nail the argument one way or the other and we are left to speculate on whether the accurate details that occur in Hamlet and other plays were based on direct observation or on a careful gleaning of information from books and from people who had returned from overseas trips.
Either way, Shakespeare's skill was in his ability to see - or hear - details and use them so deftly in his plays to give them a hauntingly poetic-authentic atmosphere.