I'm not going to write about the main tourist sights/sites (apart from the stunning Cathedral) because there is ample information on Vt about these already.
But do walk the old part Toledo, as much as you possibly can. It is a truly ancient settlement and you will, if you keep your eyes open, see much evidence of its antiquity.
There is so much to see: varying architectural styles over the centuries, chunks of Roman masonry embedded into later walls, Medieval stone doorways, azelujos tilework, tiny narrow Medieval streets barely wide enough for a car (it's fun to watch people trying to drive along these), post-Medieval mansions, mudejar brickwork, vast monasteries and convents, Medieval synagogues and even earlier mosques, intricate Gothic carving on the exterior or the cathedral...so much to see.
I spent 6 hours wandering Toledo, only going into the Cathedral, one synagogue and one mosque. I still feel I barely scratched its surface; evidence of its past is everywhere.
So walk and walk and walk: you will not regret doing so!
There are 4 different walking tours you can take around the city. You can either do these walks yourself or go to the Visitors Information Office at the Puerta de Bisagra gate to enlist the help of a guide. You can obtain a map from www.go-toledo.com/walks.
Go back hundreds of years and walk through medieval Toledo.
Drop into a church... dark, candle-lit full of gigantic baroque paintings pre-dating El Greco and inspiring him.
Each winding alley-way will eventually lead you back to the city square full of bustle, bars, tapas, restaurants.
Just wonder... costs nothing and is a remarkable experience.
The narrow stone-paved streets of Toledo may offer you more than you expect. Be ready to catch some nice photos like the cat in the vase in one of the balconies...
As soon as you arrive to the train station ask the city walking tour map. With this map you will make a nice walking tour