Most climbs are called
The longest climb in Flanders is the Hotond or Hoogberg, near Ronse at 105 m/344 ft (total height 159 m). All of it is alongside major roads. The nearby Knokteberg aka Cote de Trieu, situated near the language border, is a much more scenic climb on a smaller asphalt road starting in Russeignies. It climbs 92 m /301 ft over 1,260 m or three quarters of a mile.
Most die-hard cyclists have heard of the Oude Kwaremont, the Paterberg, the Muur/Kapelmuur and the infamous Koppenberg so I won't review these here. Instead I will focus on some other fun climbs that are easily accessible from Oudenaarde or nearby locations.
The infamous Koppenberg. Don't worry it looks much better now!!
One of my all-time favorite climbs is Nokereberg, a cobbled quarter mile (350 m) climb through the center of Nokere, a part of Kruishoutem. It is famous because of Nokere Koerse and other races that end here. The average grade is 5% and the road climbs 20 m or 66 ft. It is part of the blue loop (blauwe lus).
For something a bit more challenging, try Tiegemberg aka Vossenhol, a stretch that has been in the Ronde 20 times. It is a shaded, asphalt climb that is 750 m long and climbs 42 m/ 138 ft. The grade is 5% with a maximum of 9%. It is not part of any tourist route but easy enough to find when you head for Tiegem. It is a favorite with the local bike clubs.
Very close to Oudenaarde is Edelareberg, a road that has been featured 33 times and climbs 64 m over a nearly mile (1,525 m). It is an asphalt climb located in Edelare, a sub-municipality of Oudenaarde. From there you can go to Volkegemberg, another asphalt climb with 200 m of cobbles near the top, that climbs 54 m over 1 km. Also in Volkegem is the Wolvenberg, a half a mile short but very steep (max 17%) stretch that climbs 41 m/135 ft.
In favorite cobbles I mentioned the Steenbeekdries, a 700 m climb that comes right after the Mariaborrestraat located in Maarkedal, just south of Edelare. If you like punishment, you can ride a loop over the Oude Kwaremont, the Paterberg, the Koppenberg and the Steenbeekdries. You can ease into this by starting from Oudenaarde, going South along the river ("the canal") to Berchem. There you leave the canal route and climb through the village and follow the Ronde signs up to the village of Kwaremont.
If you go up the main road, you are climbing the Nieuwe (new) Kwaremont, a wide asphalt road that climbs 106 m/ 348 ft over a distance of 2,550 m or 1.5 miles. It has been in the Ronde 53 times. If you follow the orange loop signs and go left before going south, you can climb the Oude (old) Kwaremont, a cobbled climb of 89 m/ 292 ft over the same distance. Although more famous, this climb has only been part of the Ronde 37 times. Both roads join up near the top. From here you can go down a bit and then left and find the road to the Paterberg. Or continue on and climb the Hotond / Hoogberg.