That looks like some of the original cannons from Collins Barracks used to protect the city. There were four I believe, one is presented in it’s original form by the Steam Power Station at the Marina, one is set upsidedown in concrete outside Bishop Lucey Park at the corner of Tuckey Street where it was used as a boat mooring point when Cork looked like Venice. What you have there I believe is a third, although … the date is quite recent. I’d think if it wasn’t one of the cannons, it’s certainly a boat mooring point, most of that area was cris crossed with waterways at the time.