There are lots of good places to ride North of the GTA... mostly over the Oak Ridges Morraine...
On the North East, there is the route to Uxbridge... you can take Birchmount all the way North to 14th then Head East until you end up in the York Durham Line (although 10th line is less busy) then head North until you get to Webb road, head East up to the 2nd Concession and head North from there... how far North is up to you... you can also take Wag road (East) and head North again via 4th Concession all the way to Zephyr if you want. The 4th is full of rolling hills. On the way back take the 3rd Concession.
On the North, you can take Bayview all the way past Stouffville road, up to Van Dorf Sideroad where you can head East up to Leslie... go North along Leslie past Wellington/Aurora up to St Johns Sideroad where you can head East all the way to Kennedy. You can take Kennedy homeward bound where a couple of hills up the Oak Ridges await you.
If you are feeling good, you can head North along Warden instead of heading East to Kennedy along St. Johns. Continue North until Mt. Albert. Along Mt. Albert you can head East all the way to York Durham road where you start your homeward bound trek southwards. If you are still feeling good, take Vivian Road (hilly) Westbound to Kennedy where you will be headed Southbound. If you want a less intense homeward ride, take Aurora (a few kms South of Vivian) to get to Kennedy. Most folks coming from the North headed downtown switch from Kennedy to Birchmount along 14th.
There are many more routes up North... all hilly and when mixed with the ever present winds, challenging.
Check the routes above on Google Maps. You could also join a cycling club... many of them take the routes I described above.
Last edited by cyclocommuter; 05-24-08 at 04:07 PM.