A few (ahem, many now) years back having just completed my Masters Degree, I was at a point where I had a reasonable income and few out goings in relative terms. Having got into the frugal student habbits and was regularly gaming AD&D 3rd Edition with a group.
The then GM, Gez, introduced me to Dwarven Forge. A prepainted resin/ceramic 3D dungeon tile system.
Gez had an account with the then UK importer and so I was able to pick up some sets are a reasonable price and these have provided trusty service since.
Now, firstly I should issue a warning here - Dwarven Forge is Addictive! I meant it. Once you start, it is very unlikley you will stop!
Secondly it is not cheap. No, don't even try to justify it, by comparring to other makers, being pre-painted etc. By comparrison one set will often cost more than several sets of glossy card tile sets from other makers.
Its just a fact. Its not cheap. And you will need more than one set. Infact, almost certainly more then 2 or 3, or 4, or 5.
So why is it so addictive.. well, firstly partly because you do need more sets to expand things. Partly due to the fact, that its so dynamic. It does not replace imagination, but it helps. Its simple. Its well made and lasts for ages. And the colouring is very well done, it allows you to replicate, dungeons, catacombs, medievil buidings, churches, temples etc.
If you can imagine it, then you can generally replicate with. The room and passage sets, deal with the man/dwarf made terrain, where as the cave sets deal with more natural subterrainian lairs.
Having not been regularly gaming D&D or any thing fantasy or scifi for a while, my sets have gone a little under used in recent years, but they are still there and waiting. And I know they will get some more use in the future.
If you have never seen Dwarven Forge in use, or lacking inspiration, have a look here;
Some very nice layouts and great inspiration material.