Cities: Skylines

The Medical Center monument will be available to build once you've unlocked 6 unique buildings. Each unique building has requirements you must meet before they unlock. The buildings and requirements are as follows (you will need to be on a map with waterway access. This eliminates the “Two Rivers”, “Prussian Peaks”, “Pine Rivers”, “Marble Canyon”, and “Woodgarden” maps):

Lazaret Plaza - Average citizen health under 20%, maintained for 3 weeks

Mall of Moderation - Average garbage pilings per building at least 25

Court House- Crime rate over 50%, maintained for 5 weeks

Oppression Office - Unemployment rate over 50%, maintained for 5 weeks

High Interest Tower - City debt $2,000 (this means debt from a loan. You will need to get a loan and then go into $2,000 in debt with the loan active)

Sea-and-Sky Scraper - Construct a harbor and a cargo harbor

Once those buildings have been placed in your city, the Medic Center will become available. It costs $650,000 to build and $14,400 a week for upkeep. It provides the capacity for 1,000 patients and 50 ambulances.

*Personal note: I find this monument to be the most difficult to unlock because all but one of the requirements are negatives. This one can take a while.