While not an "adult" vacation as another single guy I really enjoyed my trip to europe and introduction to FKK clubs in november.  You can do whatever you want as far as relaxing or tourist stuff then go chill at the clubs for as long as you want.  Many have pool areas where you can relax and read or have some drinks.  I just found the environment really relaxing and am looking to make a trip more specific to doing a mini fkk tour in the near future.  The clubs really are unlike anything I could have imagined without seeing them.