Most vehicles look very typical both from outside and inside so no one will ever know if it is full of drugs, money, weapons or even something legal. Using a concealed compartment can have very valid and honest reasons like protection of valuables from thieves, a way not to loose something or be just a storage for junk. Obviously anyone can hide something under a seat or go a little further and make a hidden niche for example but its too simple and not an intricate job at all. A 'trap' is a hidden compartment indeed but not only finding it is hard but opening can be really tricky.
There are some known traps that were discovered by police and made public as no one would be so stupid as to reveal a really good hiding place voluntary. And there are really fascinating ones. The process of opening it is almost like a secret mason handshake or a shaman ritual so that no one will ever open it by accident. For example, one of the trap's description I found on the internet has four steps two of which are more like conditions that will prevent the compartment to open during a roadside search and that is really neat.
Here is one example of how it works: driver's seat has a pressure sensor so if driver was asked to get out and no one is sitting, compartment will not open. Then all the doors have to be closed and this makes it also impossible to open if you don't get in the car and lock it from the inside. If you got it right, sitting in the driver's seat and locked the doors you need to turn on rear window defroster and simultaneously push two window switches on the driver's door. Air-conditioning vent has a magnet inside it so to finally open the compartment you need to swipe a magnet card across the vent. Voila! It is open, hiding spot instead of a passenger-side airbag is at your service to hide your little secrets in it.
Of course with a bit of brute force and unlimited time its possible just to dismantle a car and find anything but as a precaution from any unexpected and adhoc search weather it is a lawful action or a robbery this could be of great help indeed.
If at this point you are eager to get one there are companies that install such compartments though it actually can be illegal in some countries so you should first check it out. Of course if you are a not a butterfingers person then you can build one yourself but again you should keep in mind that having illegal stuff in it is often punishable. Creator of the trap design described above, Alfred Anaya was a professional traps installer and he got some jail time for installing traps that were used in criminal activities.
People like me, on the other hand, unable to build anything with own hands, too lazy even to try or simply unwilling to interfere with a well-working machine can turn to buying cars that are equipped with sort of factory built 'secret' compartments. They are most probably mentioned in the owner's manual but who reads that stuff... Many owners find it by accident a couple of years after acquiring a car. Check yours, maybe you do not know it as well as you thought:
Prius has a hidden drawer compartment under console but its only available in Gen II Prius 2004 - 2009 version, try to check below front cup holders if you have the one.
Dodge Dart, Ford Fusion
Several models like Dodge Dart 2013, Ford Fusion Estate 2002 - 2012, are known to have a storage areas under a passenger seat. Not too secret but how would you know?
Chevrolet, Cadillac maybe some other GM
Several models have a similar feature of a hidden compartment behind a dashboard front area, this one you can find in Chevy Impala, Cadillac Escalade, Chevy Tahoe
If you are an owner of Cadillac Escalade check if you have this motorized compartment! Simple and definitely legal
Some Ford Focus modifications have a rather comfy niche
VW has a Golf with a nicely installed box drawer under a driver's seat. Similar box can be found under Chevrolet Lacetti passenger seat.
I did not find any secrets in my car, a little disappointing. I think my next car will be Dodge Ram 2019, I am still checking out but it seems to have loads of little boxes
Do you know of any cool storage spots that are factory built?