If you live in Prague, you don’t have to travel to Stonehenge to see the sun put on a show for the summer solstice.
There is growing interest every year in watching the sun set over the roof of St Vitus’ Cathedral from the Old Town Tower of Charles Bridge. This year, the summer solstice is June 21.
If you stand at that tower and look toward Prague Castle, the sun crosses the main tower of St Vitus’ Cathedral, lighting up the top chamber, goes past the small altar bell tower and sets on the roof before the edge of the sun peeks out of the church’s apse and then sets a second time on the roof of the adjacent All Saints’ Church.
To see the show, you need to be at the base of the Old Town Bridge Tower at about 8 pm to see the sun approach the Castle towers. The show is over by 8:35. The official sunset time is quite a bit later, at 9:16 pm, but the Castle is on a hill.
Clouds sometimes get in the way, so if the weather looks unfavorable you can go a day or two earlier or later to see pretty much the same effect. After the solstice, the sunset moves back toward Petřín Hill and won’t set over the Castle for another year.
The alignment seems to be intentional, rather than the result of random chance. Emperor Charles IV was instrumental in building both St Vitus’ Cathedral and Charles Bridge, and by all accounts he took astrology very seriously, as was typical for the era he lived in.
Astrologers allegedly picked the time that construction on Charles Bridge began so it would create a numerical palindrome of odd digits: 135797531, meaning the year 1357 at the 9th day of the 7th month at 5:31 in the morning in Old Bohemian time.
Charles Bridge, known simply as the Bridge or Stone Bridge when it was built, took the place of the previous Judith Bridge, which was damaged in 1342 in a flood.
The route of the bridge changed, though. The Malá Stana side remained the same, and one of the towers on that side is from the Judith Bridge era. But on the Old Town side, the bridge was moved downstream slightly. This made the bridge stronger against the current, but it also facilitated the solstice alignment.
Architect Petr Parléř worked on both the cathedral and the bridge, so he would have been in a position to make sure they lined up. One of the statues on the bridge’s Old Town Tower is of St Vitus, and he is depicted in a circle representing the sun. This creates a further link between the sun, the tower and the cathedral, which is named for the same saint.
As with all events involving the sun, it is important not to stare directly at the sun for too long. Taking periodic glances while wearing dark sunglasses is recommended, and another option is to watch the sun though the screen of your phone or camera, while avoiding directly looking at the sun.