Foreigners arrive with a neighbourhood list. Locals answer in metres. Here's why the second one is more useful, and how to read the valley by height.

Ask a paisa where the good property is and watch what happens. They won't give you a neighbourhood first. They'll gesture up the slope, or say "arriba" or "por Las Palmas," or name a loma. The mental map here is vertical, and once you see it you can't unsee it.
There's a physical reason. Medellín sits in the Aburrá valley at roughly 1,495 metres above sea level, and the city has grown up the walls of that valley rather than out across a plain. The eastern slope climbs from the river to the ridge at Alto de Las Palmas around 2,450 metres, and then drops onto the Rionegro plateau at about 2,100. Everything a buyer cares about changes as you climb.
Temperature. This is the most immediately physical one. The valley floor averages around 22°C year-round — the "eternal spring" of the tourist copy. Upper Poblado, a few hundred metres higher, runs cooler. Llanogrande at 2,100 metres is cooler again, with nights that genuinely require a jumper and houses that have fireplaces because they need them. In a country with no seasons, altitude is the only climate control you get.
Building age and type. The flat parts of the valley were built first. Laureles is largely 1970s to 1990s stock. The upper lomas were developed later, with larger floorplates, gated access and the amenity packages — pools, gyms, generators, 24-hour porters — that define the top of this market.
The view. Obviously. But it's worth being precise about what you're buying: above roughly 1,700 metres on the eastern slope, a west-facing unit gets the whole valley and the sunset. That view is the single most-photographed asset in Medellín real estate and it is priced accordingly.
Whether you can walk anywhere. Here's the trade. The valley floor is flat and gridded and you can live on it without a car. By 1,850 metres the roads are steep and narrow, there is nothing at the end of a walk, and you will drive to everything including bread. This is the cost of the view and people consistently underestimate it until they've lived it for a month.
You'd expect a chart here: elevation on one axis, price per square metre on the other. It would be a good chart. It would also be fiction, because Colombia has no public register of sale prices. There's no MLS and no queryable record of what properties actually sold for. Every "average price per m² in Medellín" figure in circulation is built from asking prices, or from one agency's private book.
Asking prices in a market with no public comparables float free of reality in a way that's hard to convey to someone used to Zillow. Two identical units in the same building can be listed months apart at prices that differ by a third, and neither number tells you what either one will sell for. This is also, incidentally, why a broker with genuine recent transaction knowledge is worth far more here than in a transparent market.
Before you tour a single property, decide where on the slope you belong. It's a narrower question than "which neighbourhood" and it does more work:
Then go and physically drive the commute you'd actually make, at the hour you'd actually make it. The loma that's beautiful on a Tuesday afternoon is a different proposition at six on a Thursday, and no amount of reading substitutes for sitting in it.
Send them. I answer real questions about real situations, and if the answer is that you shouldn't buy anything yet, that's what you'll get.
I read every message myself. No autoresponder, no call centre.