I've just watched the final episode of 'The City and the City'. Do any of you know what the caves were that it was filmed in? It could have been a set, I suppose.
Did I read somewhere that the series was filmed in Budapest? In which case it could have been in the caves under that city. I would have thought cavers would have been involved. Just to stop them setting flares off.

The final scene with all of those pillars looked familiar.

The huge underground space in the city of orciny was filmed in peak cavern.

Yes Peak Cavern
Cavers were involved and no flares were set off !!
Some incredibly bright lights were used though.
Some ?green screens? and pumped water all added to the effects.