The Campanile di Sant' Andrea (Bell tower of St. Andrea) is a very old Gothic brick bell tower with one stone integrated into the tower and one stone tablet attached to it. The one in the tower says:
A DI XI DE MAZO
MCCCCXIII
This translates to "The day 11 of May 1413". The other one attached to the tower a little higher says:
1414
TU M(ih)I P(r)INCIPIUM FI(r)MUM STABILEQ(ue) DEDISTI
AT FINEM DABIS FINE IUVA(n)TE SVPREMO
ABAS IO(a)N(n)ES CANONICE DOCTOR ORIGO
CVMARUM TELLURE NOSCITUR ESSE TUA
AN(n)I CUREBA(n)T TU(n)C CHRISTI MILE DUCE(n)TI
BIS ILLIS ADITIS DECEM CUM UNO T(r)IBUSQ(ue)
This one translates to "You gave me a solid and stable beginning, but with the help of the Supreme End you will give me an end, Abbot John, a doctor in canon law, born, as we know, in the land of Como. Then there were the years of Christ twelve hundred plus two hundred, ten with one and three.". In other words: 1414. Probably the construction started in 1413 and was completed in 1414.
There is an additional plaque with a transcription and translation (to modern Italian), made by Prof. Rodolfo Signorini. There is hardly any information about the bell tower to be found but Wikipedia says:
"The Basilica of Sant'Andrea [...] was begun in 1472 [...] on a site occupied by a Benedictine monastery, of which the bell tower (1414) remains. [...]
In the belltower there are five bells (A, C#, E, F#, A) cast in the 19th century."