King John of Bohemia is mentioned in the sources in connection with the Prague cathedral and with the city of Plzeň.
St Vitus Cathedral
According to the cathedral's website, John of Bohemia laid the foundation stone of the new church, already the third on the same site, on 21 November 1344, in the presence of the crown prince Charles [1]. The Prague Castle Administration states that construction of the Gothic cathedral was begun in 1344 by Charles IV [2].
Plzeň
According to the city of Plzeň, John of Bohemia confirmed by a charter of 8 October 1320 all the rights the city had received from Wenceslaus II, and newly set the extent of the city at 178 lány [3].