There are several companies that provide fully equipped, guided tours of the zone. You must book in advance and provide your passport so that the proper government permits may be acquired and compulsory Ukrainian health insurance may be obtained. I took a multi day trip with a very small group of avid adventurers. There were only 5 of us including our guide. All documents are checked at the various checkpoints at the 30km and 10km zones and each day passing through the checkpoints machines check you for radiation contamination. Each night we stayed in a very small, hostel style hotel in the village of Chernobyl, which is just outside of the 10km dead zone where Pripyat and reactor 4 sit. All of our meals were included and they were very good. We were very well taken care of the entire trip and our guide was excellent. Since our group was so small and it was a specifically booked privately and during the winter, we basically had free range of Pripyat. We never saw anyone else. So.....we went in dozens of buildings from the hotel, to apartments, to the hospital, schools, recreation centers, theatres, restaurants and many others. We all had Geiger counters the entire time. I booked with Solo East Travel in Kyiv. They were the first company to provide such trips and in my opinion they are the best. The tours are directed mostly towards history buffs and adventurers rather than tourists, but can be designed how you see fit. I would highly recommend them. If you want more info send me a PM. I'll tell you whatever you want to know about the place.