In Spain the solstice begins at 5:33 on the 21st
The word solstice (Sun standing still) refers to the apparent stillness of the sun for a few days from the moment of its entry into the new season, both the summer solstice and the winter solstice have had magical connotations since ancient times, the Sun, an instinctive symbol of power, would stop, and in some way it marked those born under this configuration, it is no coincidence that Christmas is celebrated in the northern hemisphere (the most populated) at the other solstice, the winter one.
Sometimes it seems we forget the cultural imposition of inhabiting the most populated hemisphere, and it is worth remembering that the southern hemisphere celebrates its winter solstice at the exact same moment that we celebrate the summer one, and although European traditions are deeply rooted (Saint John is also celebrated at the same time) they are customs mixed with their ancestral traditions, the protagonist is always the sun and its eternal return, the Sun stops and opens a door, a door of entry and also a door of exit.

The Temple of Karnak in Egypt, which by the way I visited years ago, demonstrates the importance that was always given to the solstice and the reason why its celebration endures, a festivity that was embraced by the Catholic Church transforming it into Christmas and Saint John, in Karnak it marks the importance of the birth of the Sun god Ra on the same date that we celebrate Christmas, it is no coincidence, the examples of temples aligned with the solstices are numerous, and perhaps one of the oldest and most well-known is Stonehenge, which marked 5000 years ago the beginning of summer in the northern hemisphere.
As a curious fact I leave you a web page that collects streets in cities around the world, including Spain, that are aligned exactly with the beginning of the solstice, I don't know how the author achieved such skill, but it is clear that some of these streets were laid out with full awareness, just as the ancient Egyptians or the builders of Stonehenge also did.
The bonfires
In the northern hemisphere, the most populated one and where I currently live, the tradition is to light bonfires, the day of the solstice is the day with the most light of the year, the brightest day, the symbolism is very obvious, it is the day when light is most extensive, it is the victory over shadows, the one who always wins is the Sun, a Sun that stops for a few days and begins again its journey on the night of the 23rd to the 24th, let us celebrate it.
If you wish an astrological study of your birth, or about a specific period you can contact me here, thank you!