It's a common problem: the known and best training spots are miles away from your house or you're in a new area and don't have time to travel, and you're left in an area without a great place to train. Often on videos you see people commenting that they wish they "had places that good where they could train" but it doesn't have to be a problem.
When I was first starting out, I looked for areas near me and the place I ended up spending most time training was actually a lone low short wall which looked to have very little potential but still allowed me to work on controlling my landing to be as soft and quiet as possible on simple jumps as well as it being a good spot to test out my jump distance from a wall, aiming for random spots on the ground (my thought process usually along the lines of wanting to land as if balancing on 'that tiny black piece of dirt by that piece of rubbish lying on the floor') and although it wasn't as exciting as the amazing walls of vauxhall to practice these things, it still allowed me to practice and improve my control and overall intuition about the distance i can control my body with jumps and was definitely worthwhile.
What I now appreciate and would encourage others to do is to see the potential from any obstacle around them, even just flat ground gives the ability to practice rolls, aiming for set distance and landing, working distance in strides and single/plyometric two footed jumps, aiming for 180/360 precisions and a horde of other movements which all improve through practice. A single rail can open up practice for every type of vault, balance work, various spins, landings, take off, the list goes on. By practicing attempted to make use of every obstacle, not just practicing the movements themselves, one can improve their parkour vision, helping every other element of the traceur's ability.
There really is no such thing as a bad area to train, although admittedly many places lend themselves naturally to a series of movements with obstacles located at suitable distances apart to help train close to the limit and link a wide variety of moves.
What there definitely ISN'T is a place where it is impossible to train. Conditioning with the body alone can take place anywhere so even somewhere confined should never stop progress.