The Grand Canal is the main street of Venice. Lined with beautiful, if aging, palazzo, you can hop aboard a gondola and imagine a time when these boats were the main means of transport (once there was 10,000 now there are 400). The impressive palazzo, homes to all the wealthy families, had highly decorated exteriors with colorful paintings and mosaics. These days they tend to have faded to one color but many still have the ornate, oriental facades influenced by the merchant trading with the East which made Venice rich.
Only a few bridges cross the Grand Canal: the Accademia Bridge, the Rialto Bridge and the bridge near the station at Ferrovia. Stand on these and watch boats pass by filled with fruit and vegetables, slabs of soft drink, building materials etc because Venice is still a city without cars and everything the city needs has to be transported by water or handcart.
The best way to see the Grand Canal is from on the water. Catch a vaporetto (ferry) sit out the front and take in the sights. Vaporetto 1, 82, N also 3 and 4 go along the canal. Gondolas are more atmospheric but much more expensive. Get a map naming the palazzos you pass.