This is a short leisurely walk in Killarney National Park to the point where three lakes converge: Upper Lake, Middle Lake (Muckross Lake), and Lower Lake (Lough Leane).
From the Dinis car park just off N-71, follow the flat Muckross Lake Loop trail towards Dinis Cottage. The path skirts around Muckross Lake until you arrive at Dinis Cottage, which is a tea room open during the summer season that has hundreds of rhododendron of different colors blooming in early summer.
Just before the cottage, there is a sign marking a trail that goes back to the Old Weir Bridge, which is a 16th century arched bridge over a stream. It's about a 5-10 minute walk back to the bridge from this point and it is well worth it. Explore some of the other trails past the bridge to get some great viewpoints of the Upper Lake.
To return to your car, walk back to the Muckross Lake Loop Trail and turn right. It will be about a 20 minute walk back to your car.