Osaka Castle is surrounded by water as the barrier from enemies during war. Osaka Castle has many beautiful gardens and parks, which is free of charge to enter. You may see sakura trees in the park and some local japanese who sits or picnics at the park. 
About 10 minutes walk from the parking lot, you'll arrive at the entrance gate of Osaka Castle.
Behind the gate, you'll see wide open park with an old historic building at one side and a high antique castle on the other side. The old historic building was once a museum, but no longer used. While the antique castle is the Osaka Castle Museum, which asked for fee if you want to enter.
About 10 minutes walk from the parking lot, you'll arrive at the entrance gate of Osaka Castle. 
Even though you are not going inside the museum, Osaka Castle is still interesting to look from the outside. You can even enjoy the park, alone. There are many wild birds gathering at the park, waiting to be fed by the visitors. My tips: give the birds popcorn, they'll love it and you can even take pictures with the birds on your hand.
There are some Japanese stalls and restaurants located at the park, you can have lunch there to taste Japanese foods, which I said are a little bit pricey. However, you must try the slush ice and matcha (green tea) ice cream.
After lunch, we went back to Osaka town and visit Shinsaibashi, the shopping area at Osaka, which is like a long alley filled with small shops and department stores. They have various things from fashion to music and including cafes and restaurants. The place is very crowded with people and you must walk quite far (cars are prohibited), yet the shops are very interesting to look at.
When you go through Shinsaibashi, there is one famous bridge, named Dotombori, which has many big and colorful neon signs. Dotombori has been used as shooting location of big movies as the colorful signs makes the bridge a fascinating photo spot, especially at night.
Near Shinsaibashi, there is building specialized in selling electronic goods, named Bic Camera. If you are a fan of gadgets, I suggest you to go there, as Japanese also buys electronic goods there. If not, at 8th floor in Bic Camera, there is 100 yen shop, which sold everything from home appliances to fashion accessories at 100 yen. This place is recommended if you want to buy cheap souvenirs as souvenirs at other places in Japan may be very expensive (yes, they are! believe me!). When shopping at 100 yen shop, you must be aware of chinese and low quality products.
Shops in Japan mostly are closed at 7pm but cafes and restaurants are opened till night. As for me, prices of goods sold in Japan are very expensive, for example, prices of shoes are 5,000 yen, for the type of shoes you'll find at ITC (not branded shoes). That's why I almost didn't buy a thing at Shinsaibashi, however I found Japan's stockings and make up at very reasonable price, happy! :)
xoxo,
Travellicious
