15 meters deep underground in 4 levels, not just a 15 meters long tunnel.

This misses the most important question.

Why is it for sale?

So you just go digging under neighbours properties? What about underground infrastructure?

128sqm below ground level is merely similar to a relatively small apartment: not a lot of area. I think you could get more genuinely usable area from renovating a garage in many cases. That's partly because it's more likely to have fresh air, light, and both level and long item (eg. furniture) access. Not to mention ceiling height and structural stability.

Some people really love tunnels. Personally I always wanted a house with two basements. Or maybe more. Probably inspired by the 2002 movie Resident Evil.

15 meters is a tragedy. 15 million is a statistic.

15m is… almost nothing?

It's got a lot of interesting qualities, but it looks like a dungeon… Not quite put the lotion in the basket type.. but close.