Do not put the tower on the floor, it is likely to be damaged from cleaning activities; it could easily get wet from spills or mopping and it will pick up lots of dirt and dust. It needs to be close to a power supply with access in and out for various cables and as far away from the sinks and other water sources as possible. For example if you position under the chair you will need to run monitor cables and USB inputs under the floor to the tower. If possible put it in a lockable cabinet or secure it with a cable to frustrate thieves. Stolen computers are the number one cause of re-portable data breaches.