In the morning I walked to the Buchanan Bus Station in the center of Glasgow and took the 10:30 bus to Stirling. I had bought tickets in advance but there was only about 10 old people on the bus. It's only a 30 minute ride to Stirling.
The Stirling bus station is in the center of the village and from there it's an easy 10 minute walk to the castle. There is some really nice architecture along the way, maybe Victorian.
The castle is a mini version of the Edinburgh Castle with different buildings and halls. They're both just clusters of buildings at the tops of hills.
After spending about an hour at the castle I hiked the 4 kms to the Wallace National Monument. It's a nice walk and crosses the Firth River on the historic Stirling Old Bridge, a medieval stone bridge from the 1500s.
The Wallace National Monument was under construction so people weren't allowed inside but the grounds were open and free to enter. There are nice views of the city and castle from the top of the hill near the monument.
From there I took a local bus back to the city center and main bus station to go back to Glasgow.