Gniezno was one of the first Polish capitals. Here, the first Polish kings were crowned.
According to a legend, many many years ago three brothers - Lech, Czech and Rus - decided to explore the northern-eastern part of Europe looking for a good place to settle. Lech decided to start his kingdom on a hill with an old oak and an eagle on top. He picked the white eagle as his emblem and because of the eagle nest (in Polish, nest = gniazdo) to call it Gniezdno (today: Gniezno). The other brothers went further to find a place for their people. Czech went to the South, where he found Czech Republic, and Rus went to the East, where he found Ukraine.
Around 940 AD Gniezno became one of the main fortresses of the early Piast rulers and around then Mieszko I (Prince of Poland) is thought to have moved the capital from Poznan to Gniezno. (From there the capital was later moved to Cracow).
Gniezno cathedral was a royal coronation site for the first Polish kings: