The Vinobraní: 'I am Hannibal!'

Today's picture is one of several extraordinary spectacles at last weekend's Vinobraní, or wine-harvest festival in the Grébovka park which borders Vršovice and Vinohrady. Just after my friends and I arrived, a great trumpeting was heard, and a fully costumed warrior rode in on the elephant roaring out 'Ja jsem Hannibal!' at the top of his voice.

The elephant was then led in triumph around the park, which also bore witness to archery contests, gladiatorial fire fights, and a huge crowd of people sampling the flavour of the year's first burčák.

Burčák is partly-fermented grape juice - the preliminary stage of the wine-making process. The extremely sweet and potent liquid (between 5% and 8% alcohol) is sold in one-litre plastic bottles and consumed throughout the afternoon. This innocuous-looking drink (it reminded me of slightly fizzy pear juice) is so refreshing in the late summer heat that many unsuspecting drinkers are legless by the evening.

At the point when I took the picture, the elephant was also going down on his knees, though l'm not sure it was the burčák in his case; I rather think he had been trained to do the trick - but who knows?

Putting things in perspective

Today's picture is not from Vršovice at all, but from Holešovice in Prague 7. That's just about as far as we have ever ventured in these pages - but there's a good reason for the journey. Today is theme day on City Daily Photo, a splendid website which aggregates photo diaries from all over the world and publishes the main pictures side by side, so you can see what's going on pretty much anywhere at a glance. And the theme for September is 'Perspective'.

A few weeks ago I paid my first, long overdue, visit to Dox, the newest - and one of the most successful - of Prague's contemporary art galleries. Here we can see 'Zig Zag Corridor' by op-artist Petr Kvíčala, an unbroken 10cm-wide red line painted directly on the walls of the gallery. The idea is that when viewed end-on, the rectangular lines start to reveal diagonal 'zig-zag' paths, which emerge in a ghostly way from the design. But to me there's a further illusion. Can you see how despite the straightness of all the lines, the walls of the corridor appear to curve or bulge out slightly? Only one person could answer my query, my friend David, a specialist in optical illusions. He told me what was going on:

'It's the Hering illusion, a special case of the more general Zollner illusion. In both, the short cross lines usually extend either side of the long lines that seem to bulge or lean over, but, as here, the effect works even if an edge just abuts an array of short obliques.  Amazingly, it was first reported in the edges of the feathers of arrows by Montaigne.' So, now you know!

Click here to view thumbnails for all participants in today's City Daily Photo theme day. Or, for more optical illusions, please visit David's site here. And now I'm feeling just a bit dizzy, so I'm off for a beer to set things straight again.

Jára Cimrman

Jára Cimrman was a celebrated Czech writer, inventor and explorer. Born in Vienna in the 1860s, his expertise was highly valued in his lifetime, even though subsequent history has not always recorded his outstanding contributions. Among the many great names assisted by or influenced by Cimrman were Thomas Edison, Count Zeppelin, and Marie Curie. It is quite astonishing to realize that many of the inventions we take for granted today, even the humble light-bulb, would not have come to fruition without Cimrman's input. He advised Gustav Eiffel on the location of the Eiffel tower, and helped Chekhov write his plays. He also very nearly discovered the North Pole. And recently it has been claimed that he developed prototypes for both the CD (the Cimrman Disc) and the Internet.

Since 1966, when his papers were re-discovered, Cimrman has been the subject of multiple books, films and radio programmes; and a long-running series of biographical plays are continuously enacted at a playhouse uniquely dedicated to his exploits, in the neighbouring suburb of Žižkov (Prague 3).  But today's photo comes from the south of Prague, from Michle (Prague 4), and shows a sign affixed to a hotel where the famous man once breakfasted.

Needless to add, Cimrman is a fiction, the brilliant invention of the equally polymathic, but real, Zdeněk Svěrák. But the enduring popularity of this Quixotic figure has made him one of the most popular figures in Czech history, as proved by the fact that he was voted the Greatest Czech in a TV poll in 2005. When Czech TV disqualified him on the grounds that he was not an actual person, there was a massive public outcry, which saw Cimrman rightly restored to first place, albeit in a special category all his own. He would have been delighted.