It is not known exactly how long the valuable liturgical instrument was hidden in the recess in the wall, as the Kathpress press agency reported on Thursday.
According to Slovakian media reports, church rector Jozef Gallovic said that the chalice was listed in an inventory list of the parish from 1857 as the oldest chalice in the basilica's furnishings.
Gallovic assumes that the chalice was hidden in the early 1950s for fear of persecution in the then communist Czechoslovakia. In future, it is to be used again at church services.
Not all mysteries solved yet
The chalice dates back to 1520, as is noted on the back. It is richly decorated: the foot, knob and dome are adorned with floral ornaments and cut red stones. Below the knob are six finely crafted figures of the risen Christ and an as yet unidentified saint.
Experts from the Slovakian Monuments Office want to have the chalice entered in the register of national cultural assets.
This is not the first treasure to be found in the late Gothic and later Baroque basilica in Trnava.
A Baroque monstrance from the 18th century was discovered in the organ's wind tunnel back in 2005.
In times of need, such as during the communist regime, valuable artefacts were often hidden to prevent their destruction. It is therefore expected that further sacred artefacts will be found.
Every year in November, St Nicholas' Basilica is the venue for the "Tyrnau Novena", which commemorates a procession in 1720.
At that time, people prayed for protection from the Turkish threat and the plague.
The miraculous image of Our Lady, which was honoured in the procession, is displayed on the high altar during the nine-day week of remembrance.