Bayer: first ever team unbeaten in Bundesliga season!

By winning the last round game vs Augsburg (2-1), Bayer Leverkusen became the first team in the history of Bundesliga since its founding in 1963 to go through the entire league season without defeat (28 wins, 6 draws in 34 matches).
In the history of the European top 5 leagues, there are 8 such cases. Previously, three of them were noted in Italy, 2 in England and 2 in Spain. The last time this happened in 2011-12 (Juventus).
The table lists these feats in chronologic order.
In England, an unbeaten team (Preston North End) triumphed in the very first season of the newly established league. Subsequently, only Arsenal under Arsene Wenger managed to repeat such success in 2003-04.
The only team that failed to win the league title in a season in which it avoided defeat was Perugia (2nd place in 1978-79).
Real Madrid, during their invincible season (1931-32), temporarily lost the royal part of their name and was simply called Madrid, due to the fact that a republic was established in Spain at that moment.

1Preston North EndEngland221841888–89 
2Athletic BilbaoSpain181261929–30Fred Pentland
3Real MadridSpain181081931–32Lippo Hertzka
4PerugiaItaly3011191978–79Ilario Castagner
5MilanItaly3422121991–92Fabio Capello
6ArsenalEngland3826122003–04Arsène Wenger
7JuventusItaly3823152011–12Antonio Conte
8Bayer LeverkusenGermany342862023–24Xabi Alonso