In reality, nobody is careful about making this distinction. The American Heritage dictionary lists "historic" as one of the meanings of "historical," so it is not really an error to use "historic" to mean "historical."
When you are writing, follow the usage you've described. Say "historic" if something important happened there, "historical" if it is an older or more original part of a city, and "historical" to mean "related to history."
Tourist brochures use both words.
If you want to be sure that your tour takes you to places where important events happened, rather than just touring a part of a city with old buildings and architecture, you just have to read the brochure and judge for yourself.
Here's a typical example of usage: "Today, the historic F. Holland Day House is listed on the National Register of Historic Places and serves as the headquarters for the non-profit Norwood Historical Society."