Under the Trenčín Castle, in the area of the parish church, there is an intact Gothic building - Ossuary of St Michael. It was built in the second third of the 15th century as a ossuary and its rear wall is linked to the original city fortifications. Later the inhabitants used it as a chapel. Nowadays, it si very popular among visitors of Trenčín and history lovers and that is why there is a permanent exhibition.

The exhibition is installed on two floors. On the ground floor, there is an armory section, in which balls were cast in the past. On the first floor, visitors will find a cross-section of sacral objects from the Gothic and Baroque periods that come from the collections of the Trenčín Museum.

There are several fragments of sacral architecture in the niches opposite the entrance - statues of gold-plated angels - putti and some rare statues of saints. The exhibits are accompanied by panels that provide visitors with interesting information not only about this place, but also information related to the history of the parish church of the Nativity of the Virgin Mary on the Hill of Virgin Mary.