EyeC. Please expand more on your thinking with reference to:
"And I as a civil engineer I give most buildings a life span of 15 years as a safe estimate when I calculate my ROI"
Why 15 years?

On Berlin property, it depends where you look. You should be able to get property for around £1k per m2 in areas that aren't particularly desirable (but that may do well if regeneration takes place.) More upmarket areas are more expensive. Think you are talking about nearer the £2k per m2 mark there.

On Dubai, its not an area I've considered in depth. When short listing areas to look for property I discounted Dubai on the basis that it had already seen terrific increases in house prices. My feeling was that I had missed the most significant price rises. I also disliked the way attention in Dubai was going from oil to property. Were dwindling oil stocks the only reason for switching the focus to oil? Rising sea levels were also a concern. But as mentioned earlier, I didn't research Dubai thoroughly, simply did an hour or two on each of a couple of dozen countries that had caught my eye (of which Dubai was one) then whittled it down to 10 or so. Places I liked the look of and invested in include Estonia, Latvia and Morocco. Other areas I'm interested in include Montenegro, Poland and Sri Lanka, though I'm probably too risk averse to take the plunge with the latter, even if things look like they will become more stable their.