Key to the ancient past?

Beneath a jewel-blue sky, this strange stone shape shows where a building existed in earlier times.

The site is Clonmacnoise on the River Shannon. Occupied since at least the sixth century and frequently sacked, this fascinating centre of Irish heritage is located in County Offaly in the midlands.

Perhaps the remains visible in these pictures are related to the recently discovered Clonmacnoise bridge, built across the broad and shallow Shannon in the 8th century CE.