How I use captcha without making my users complete the barely readable word

What I wanted was to have the commenting feature protected against spam bots without having the innocent human users ruining their eyes on captcha like images, or complete any mathematical equation or any other additional question fields.

One very important difference between a spam bot and a human using a web browser is that the first can't run JavaScript code. However, this isn't a perfect criteria of selection, because there are humans browsing the web using browsers without JavaScript support (Opera Mini for mobile devices for example).

My ideea (and as I did some Google searches, I found out other people had similar ideas) was the followig algorithm:

Does the user have JavaScript enabled?
If yes, he's ok. Let him comment.
No? He's a suspect. Read him his rights and give him the ultimate "are you human?" test.

Put your city on the map in 4 layers. Create an artistic old map of your area.

Here's what you should be achieving: