If you're looking for a great place to spend the night, head to the American Trade Hotel, which has an exceptional cafe, restaurant, bar, pool and jazz hall. Also, the rooms are beautiful and extremely comfortable. On my last night I treated myself to a casual night at the bar followed by a concert performed by the Berklee Global Jazz Institute.
The hotel used to be a major housing spot for local gang members, but ATH has now hired some of these ex-members to give tours of Casco Viejo. It's actually quite worth it!