I'm not familiar with the site you've shown but I'd say the carvings are late 10th to mid 11th century although the vaults themselves look like modern plaster, probably not over the original material. By the time this was built it had been common to use vaulting, including ribbed vaulting, for about 1,000 years.

Vaulting offers improved structural efficiency, is far more fireproof - an important consideration for important buildings lit only by open flames, and it allows larger spaces to be opened inside structures. It is also visibly advanced, if one has never seen complex structures before. The awe with which early 'Gothic' buildings must have been viewed by those fortunate enough to see deep inside them would surely have been tremendous to behold.

While ribbing is often considered to only be part of the Gothic style it is not. 'Groined' vaulting was a common feature in Roman buildings (the 'edges' of the vaults butt against one another unadorned) although there are also ribbed examples that demonstrate this 'Romanesque' feature's genuine Roman origins.

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Pevsner N, 1972, An Outline of European Architecture

Theodossopoulos, D 2010, Development of Gothic vaulted space and perception of technology in the cultural role of architecture. University of Lincoln , Lincoln (Link)

Ulrich, 2014, A Companion to Roman Architecture