Midiface 16x16 : Probably one of the best midi interfaces out there.

When a zombie apocalypse strikes, this midi interface could save your life. Casing build like a tank.

Insides... I am not sure. Something moves and rattles inside my unit when I move it or shake it a little. Despite this, the device works properly in the rack, so far. I don't want to open it (don't want to void the warranty), so I don't know what was flying around inside.

If you have a lot of hardware synth this interface does everything you need, even if you transmit on 256 midi channels at once. It sends and receives signals without errors (including sysex) even with a very long midi cables. Clearly a quality engineering.

It hides all the 16 ins and 16 outs at the back.

Works out of the box with Windows, MacOS and Linux (I checked).

This interface is probable your best choice if you are looking for a professional, versatile USB midi interface with lots of inputs and outputs for a computer running OS of your choice, and want to keep all that midi cables out of sight.