Training while on Vacation

I will be traveling some in October and wonder what everyone does for training when on vacation and the hotel has no gym. I do not want to go more then 2 days without some kind of training. I will be in London, England for 5 days (Im from Texas) and will not be familiar with the area. Should i just run where ever my feet take me? I am guessing I will have to keep it to running since I can not take my bike and not sure where any pools or gyms are. Just curious on what others do in these cases. Maybe aerobics in my room?