I'll assume you don't have the Planes of Power Expansion. But even if you don't, unless I'm wrong, the Plane of KNowledge is open to everyone now.
Don't know what city is your hometown, but at each one, there's a book you click to go to PoK. Once you get there, find the stone that says The Nexus and click it. Voila!
As far as Wizzy spires you can GET to, there's one in Greater Faydark, North Karana and Toxx Forest.
There's also one in Dreadlands, but I'd doubt you're high enough level to get to it, and unless you started an Iksar, it would be out of your way anyhow.