While Tonduff is a flat boggy summit it is useful because it can be incorporated into various longer walks. It's east side and the east extending ridge it has towards Maulin are steep when facing north in places.
Two obvious approaches to Tonduff are from the east and the west respectively. From the west park in the Crone Wood carpark O1920 1417 A and walk on forest tracks to O 181 141 Bfrom then up a shoulder SW to the summit.
From the west, start from the nearby R115 for example from Liffey Head Bridge at O137137 C from which it is around 2km over rough ground to the east. Linkback: https://mountainviews.ie/summit/206/comment/4966/

Parked car at Access road at base of Kippure O1413914164 D (Room for 4-5 cars here).Took a direct course bearing 106 deg toward summit across very wet,boggy and knee high heather filled terrrain(1.9Km). Reached open flat summit (O1594413686 E) after approx 45 mins which was marked by a mere gathering of stones atop some raised bog.Excellent views in all directions of War Hill,Djouce and Maulin to the South and Kippures mast to the NorthWest.Retraced steps back to car in a round trip of approx 1 and a half hrs. Linkback: https://mountainviews.ie/summit/206/comment/6586/

Tonduff is usually described as a dull, unexciting top, but a good approach can make amends for that, and the rugged Ravens’ Glen offers at least three of them. (Ravens’ Glen is the name given in the Harvey Map, though not in the OSI, to the little valley that some glacier chewed out of the eastern side of Tonduff. It lies within the square kilometre that has O 170 130 F as its lower left-hand corner.)

The first and easiest route starts just beyond where the forest track from Crone car park (Glencree) passes over the stream issuing from the glen. Crossing the stile to the left (O 181 141 B), one has only to follow the narrow track along the granite wall on the north side of the valley up to the shoulder at O 175 142 G, before striking out slightly south-westwards, firstly over sharply rising ground and then over bogland, to nearby Tonduff.

Calling for a bit more exertion, a second approach begins on the south side of the glen, across a wet hollow that is accessed from the forest track at O 180 136 H. At the head of the valley here, a clearly visible ramp and gully, usually with a negligible flow of water, leads upwards. Where it narrows at the top, the high vegetation closes in and tends to hamper but not prevent progress.

The third approach is the more challenging. Again, starting at the above-mentioned stile, one follows the ferny meanders of the stream that flows from the Glen, right up to the steep headwall. The photo shows this upper section, with its double waterfall. It is possible to push one’s way up onto the next level through the vegetation on the left-hand side, but just out of the picture, further to the right, the steep, smooth granite shelves down to within a manageable 6 ft of the ground. If you have a companion with you, a leg-up will get you started. If you haven’t, I found that throwing my rucksack onto the rock above, with my wallet inside, gave me all the incentive I needed to get over the obstacle. Once above, the climb continues over very broken ground, with rocky outcrops and thick vegetation but otherwise no insurmountable barrier. From the rim, the remainder of the way to Tonduff, directly west, is a 1 km walk over gently rising heathery ground. I don’t suppose this third approach to Tonduff, and maybe not even the second, will fall within every walker’s comfort zone, but if you’re in search of interesting alternatives and don’t mind roughing it a bit you won’t be disappointed. Linkback: https://mountainviews.ie/summit/206/comment/3203/

Tonduff is described on the OSI sheet 56 as being in two parts, Tonduff North and Tonduff South. Both have little visual appeal to the walker, though they are parts of various popular routes. The original name of Tonduff (black backside) adds little allure either. Geographically Tonduff is interesting because the sources of three East coast rivers start on the southern flanks of the mountain: the Liffey, Dargle and Avonmore.
The composite photo was taken during a circuit of the Glencree Valley in December and shows an unusual, carved rock to the east and south of the summit. Linkback: https://mountainviews.ie/summit/206/comment/248/