The Electricity Supply Board (ESB) operates the lock that takes boats through the hydroelectric power station at Ardnacrusha, on the lower reaches of the River Shannon. The lock is, in Irish waterways terminology, a double: a staircase pair, which counts as one lock, with a combined drop in the two chambers of about 100 feet.
It's not the deepest lock in Europe by any means (although it is by far the deepest in These Islands: five times the depth of Tuel Lane) but it is relatively small, a fact that enhances the impressions created by a passage through the lock. I've put up a page of photos and information about the lock at http://tinyurl.com/ltj2b7 or http://preview.tinyurl.com/ltj2b7 or http://irishwaterwayshistory.com/about/irish-waterways-operations/the-esb-lock-at-ardnacrusha/ bjg
