The name 'Kupala' comes from the Ukrainian word 'kupatysya', which means 'to bathe'. The festival is closely linked with water - especially rivers and streams - because midsummer is also when the rivers are full and warm enough to splash about in. In some villages, people gently sprinkle water on each other as a friendly summer greeting.
One of the loveliest traditions is making flower wreaths. Girls weave wildflowers - daisies, cornflowers, poppies, chamomile - into a circle small enough to sit on top of the head. The wreaths are bright and beautiful. After a day of dancing, girls float their wreaths down the river, sometimes with a tiny candle on each one. From the bank, hundreds of glowing flower circles drift away on the dark water.
There are bonfires too. Friends gather around them, sing songs, and play games. One of the traditional games is to jump over the fire holding hands with a friend - just over the embers, not the flames. Children watch carefully and clap when the older ones go.
The whole festival happens at the time of year when summer is at its strongest. The plants are at their most green, the days are at their longest, and Ukrainians have celebrated this brilliant time of year for thousands of years.