The Professor Falls is one of the famous Canadian classics, and is very popular. The name is a pun that comes from Professor Eckhard Grassman, one of the first ascensionists, who took a fall there in 1974. This route forms early and usually lasts until late into the season. However due to the constant water supply it can be very wet, even in cold temperatures. The climb consists of three steep pitches (WI4), a gentler fourth/fifth (WI3/3+) and a final crux WI4 pitch of ice often in excess of 85 degrees steepness. Due to the stepped nature, it is common to have many parties on the route on weekends, and most consider it reasonably safe. It is best to avoid this unnecessary risk and not climb below others. We did have a visiting US party climb below us on a weekday, showing the popularity of the climb. When there is no snow covering the steps, ice slides over the lower pitches. It's not a question of "if" climbers knock down any ice, but "how much" - so make your own choice on whether you're comfortable with the risk.
The route does have avalanche hazard like the majority of climbs in the Canadian Rockies, so check the conditions from the Canadian Avalanche Association before you go. Read this accident report to see an example of people who got very lucky. There have been many other incidents on this climb, check the Alpine Accidents in Canada section for Mt Rundle. In 2007, there was a size 3 avalanche debris pile about 100 meters before the last pitch (climber's right).
Most parties rappel the route but a walkoff exists to the left. The full length of the climbing is 280 meters, so don't expect a short day.
There has been a recent (newer than guidebook) road closure and the access to this climb entails about 7km of road and good singletrack trail along the Bow River. We used mountain bikes and it took us 30 minutes to reach the base in good conditions. When there is fresh snow to deal with, this will take more. Walking would be over an hour (1h20min?) of very boring going, so borrow a bike if you don't have one.
Drive down the main street in Banff, go over the river bridge and take your left (east, as for the Banff Springs Hotel). Soon you'll come to a left turnoff and sign for "Bow Falls", a popular tourist spot in summer. Drive along this road for a few hundred meters and you'll come to a road barrier and a parking lot. Take out your bike, go through the barrier and bike along this road (always packed down from parks vehicles' tracks). Just past a clearing, the road through the golf course forks - take a right on the smaller road (if you go left, you'll reach a wastewater treatment plant, and you've gone too far!). You will eventually reach a spot where a trail turns off to your right after approximately 3-4km, where there's a large sign and map. Follow this singletrack trail for another 3km along the Bow River. You will get to a drainage with the lower part of the climb visible on your right. Stash your bikes and walk a couple of hundred meters up to the base.
The first three pitches are WI4 and have bolted anchors. The first one is short and has a bolted anchor immediately on the left.
The second pitch is wide, and after the steep part is done there is a bolted belay on the left. With 60 meter ropes, keep climbing further up a WI 3 step and flat ground to fully stretch the rope out to a bolted anchor on the left.
The third pitch has a large rock on the left, where the easiest line usually lies - a neat feature, you can almost rest your back while 'squeezed' underneath if you take such a line. Two new rappel bolts exist (2007) on a rock straight ahead - look for them.
A short walk (trail your ropes) takes you to the fourth pitch (WI 3). Climb a short step, then walk to a wide curtain of ice. Climb the right side to a cave half-way, where there is a bolted belay.
The fifth pitch (WI 3) climbs the rest of the curtain and then another short ice step to a bolted belay on the left (the bolts are quite high on the rock and can be difficult to reach).
From there, a 200-300 meter snow slope leads to the base of the last pitch (usually crux). This pitch is about 40 meters in length, and usually sports ice in excess of 85 degree steepness. Its difficulty can vary, but it tends to have bad ice with less than perfect protection possibilities. If you are confident on WI 4 it should not be a huge challenge, but this pitch still seems to turn back a lot of people. There are no bolts at the top, but there is a fixed threaded anchor through the rock with rappel rings.
From the top, most people rappel the route. You may want to solo up easy ice on a gully on the left (flat, and a couple of WI2 steps) to get a good look of the area. On your right, on the upper face of Mt Rundle, are three hard Canadian climbs - The Terminator (WI 5+/6+), The Replicant (WI 5/6+) and Sea of Vapours (WI 5/7). We watched a party of two make progress up the third pitch of Sea of Vapours, and it was quite entertaining. There is a beautiful view of the Bow Valley in the other direction.
When you get enough, rappel the route. There are bolted anchors the whole way, but they can be tricky to find. As an alternative, you can descend steep ground through the trees on the left, but a number of short rappels off trees are required according to the guidebook.
Two 60 meter ropes, regular ice rack, several pairs of gloves and Goretex to keep the water at bay. A pair of radios are useful for communication.