New York City
Houston: Best free things to do in Houston?
check out Houston on the cheap website: http://www.houstononthecheap.com probably you can find something interesting in their calender. Also check the calenders of Miller Outdoor Theatre, Discovery Green and Market Square...
Istanbul: Tips and suggestions for visiting Istanbul with my parents
You should try to visit the touristic places e.g. Grand Bazaar, Blue Mosque. But I would recommend going to Prince Islands as they will be particularly beautiful during June. Before passing to the islands via ferry, you can also...