What to do with a month of free time?

I am in second year and secured a summer position, however it doesn't begin till June. What are some things I could do with a month of free time that would make me more employable or just be really fun?

I want to sublet my place over the summer so summer classes aren't really something I want to do.

I an open to taking a trip, but it would have to be on a student budget. I have a vehicle but its kinda old and I wouldn't trust it to get me across the country. I'm not 21 so I don't really want to go to the US but it's not out of the question.

Anyways what would you do if you had 31 days of free time?