Inverary Jail, Glasgow
Inveraray jail is nowhere near glasgow. It's a 150 km round trip - go for the trip, which is always scenic, but skip the jail which is nothing more than an old country police station with some dummies dressed up in old clothes and a fake gallows - a dull attraction in an even duller village.
Fun Alternatives: It's better to travel hopefully than to arrive. Hire a car and explore the West Coast via Loch Lomond up to Oban. In the city, check out the Burrell Colection in the South side for world class art history.