This stern riverside fortress is the centerpiece of Limerick's historic area. It dates from 1210, and may have been ordered built by King John of England. The low-slung gray-stone structure is a good example of medieval architecture, with distinctive rounded gate towers and thick curtain walls. Over the years, the castle has not always fared well, though. In an astonishing piece of historical vandalism, its ancient courtyard was filled up with cheap, modern houses during the mid-20th century. Happily they're gone now, and a recent €7-million restoration has put the castle back into better condition -- but unfortunately, there's just not much to see here. Aside from a poorly explained archaeological excavation in the courtyard, the rest of the structure has little to offer. Access to the actual castle structure is limited, and what you can see is not well used. Worse, the big, modern visitor center serves mainly to ruin views of the castle, and it justifies the high admission price with a sprawling display of mannequins in period costumes and one of the most overwrought and historically simplified visitor center films you'll see on your Irish trip. The simple fact is, King John's Castle costs more than it's worth.