We can be reached by subway through Subway Line 6, Republica Argentina, and Nuevos Ministerios (Lines 6, 8 and 10) as depicted on the map. In addition there are bus lines coming and going to Sol and Callao.
Instituto de Física Fundamental.
From the airport
Barajas airport has four terminals. As described in the homepage of the airport, all terminals are conveniently connected to the subway Line 8, which ends up in Nuevos Ministerios, close to the institute. Another alternative is to take a taxi to go to Madrid, but it is more expensive and it can be a rather long trip depending on the terminal and on the traffic conditions.
Tickets are valid for both subway and bus and can be purchased at the machines and ticket counters in the subway. The price varies between 1.5 euro for a one-way ticket and around 12 euros for a ten-trip ticket. Please note that you have to stamp the ticket prior to entering the subway or the bus, and that a single stamp allows you for only one trip -- unlike in other places, every time you switch means of transport you have to purchase or stamp your ticket again. If you take more than five means of transport a day, you should consider buying a tourist ticket valid from one to seven days and unlimited travel.