Grography:

Like Tokyo, Osaka is built next to a bay, as it was also originally a major shipping city.  

Landmarks:

One of the most famous landmarks in Osaka is Osaka-Jo (Osaka Castle).  Although the original castle was largely destroyed by a fire, it has been rebuilt for tourism purposes.  Osaka castle is surrounded by a park, and often has a selection of traditional food vendor carts available in the area.  There is a river next to Osaka castle, and boat ride tours are given as well, so it's easy to make a day of a visit to Osaka castle.  (If you want to see a more authentic castle, you can visit the nearby Himeji Castle - Himeji is accessible from Osaka by Shinkansen).

Another famous landmark is the Temmangu Shrine, which is located near the largest traditional outdoor shopping area in Japan.  Osaka is also home to Universal Studios Japan.

Economy:

Nomura, Panasonic, Sharp, and Sanyo are among the famous companies with headquarters located in Osaka.

Similarity to Tokyo:

Osaka, being a large metropolitan center, shares much in common with Tokyo.  It differs more in style than in substance.  For example, it has districts similar to Akihabara and Shinjuku, and many other places that could be seen as "sister cities" to locations in or near Tokyo.  As mentioned above, they are both located along bays, and both have several major rivers flowing through.  Both areas also have excellent mass transit, including local commuter trains, and Shinkansen (bullet trains).  The closest analog to the Yamanote line of Tokyo is probably the JR Osaka loop line.

Despite the similarities, Osaka does have a cultural flavor of its own, and is certainly worth a visit.