Things to See:

Metrocable (to Parque Arvi)
Communa 13
Guatape
Medellín Museum of Modern Art (MAMM)
Botanical Gardens
Guatapé (It’s a day trip, but worth it)
Mercado del Río
Centro Comerical Palacio Nacional (Commercial, but if you need to do shopping you can here)
Plaza Botero

Restaurants:

Mondongo’s
Carmen
Alambique
Idílico
La Pampa
La Causa
Pergamino Cafe – Go for the coffee 
Rito Y Monteo

Bars:

El Poblado (also a great place to stay) is probably the biggest area in Medellin, specifically Parque Lleras which is treelined, a lot of bars, and just fun. Also fun in El Poblado which is like a subsection of the neighborhood is Provenza where there are some more chill bars and good restaurants. Laureles is another party area (La 70 is the main street where there are bars on either side of the street). Avoid the city center at night, it’s pretty dodgy. Just north of El Poblado in Barrio Colombia are where alot of the more bougie clubs are. Finally ill mention Las Palmas which is above the city so you need to take an uber. Las Palmas also has some pretty exclusive clubs and the views of the city are amazing. Normally if you’re going there you’re going to spend the whole night there. La Strada is also cool, it’s a mall with multiple levels with bars and shops around it.

37 Park – Very cool garden

Yacky Chan

Altagracia

Calle 9+1

Rooftop Bars:

Sky Bar

Mosquito Rooftop

Envy (The Charlee Hotel) – Similar to Mr. Purple in NYC if you’re familiar.

Woka Lounge

Clubs:

Babylon (Thursday Nights first 100 girls free)
Gusto
Salon Amador
La Chula
La Oculta – Pretty cool, kind of a speakeasy where you enter behind a bookshelf (in Provenza)

For late nights, i have ended up many times at clubs on the intersection of Calle 86 and Carerra 42 AND Discoteca Palmahia (right next to eachother)