The best way to reach CIEMAT is by bus. Line 82 has a stop close the main CIEMAT entrance ("Paraninfo/CIEMAT" stop). Walk back 50m on the opposite sense of the bus (see image).
The starting point of line 82 is stop 1329, MELENDEZ VALDES-PRINCESA, close to Moncloa Metro station.
You can use this tool for a detailed route. The price for a single bus ride is 1.50 EUR, and can be payed directly to the driver (you better carry the exact change). 10-ride tickets are available, but can only be purchased in the automatic machines at metro stations. These 10 trip tickets are valid both for metro and buses.
The Madrid Metro is an extense network, and probably the fastest and easiest way to move around town. Ticket prices depend on the route. The closest Metro station to CIEMAT is “Ciudad Universitaria”, line 6 (grey circular line). From the station to CIEMAT there is a 15 minute walk (1.2 km). Follow this itinerary to reach the center.
The fare for a ride between the airport and any point in the city center (CIEMAT included) is 30 EUR, fixed rate. It takes 20 to 25 minutes, depending on traffic conditions. The address is Avenida Complutense 40.
During the workshop, reaching CIEMAT by taxi might be also a convenient option for 2 or more people. A ride from Moncloa to CIEMAT should cost no more than 4 EUR
Upon arrival at CIEMAT, proceed to the guardian lodge at the main entrance and identify yourself, mentioning you are attending the RED LHC Workshop. If you are registered for the meeting, they will have your data and will show you the way to the conference venue. Signals will be attached in several points to guide you. An access badge will be issued at the entrance, it will be valid for the whole wokshop. The meeting will take place in the main auditorium of building 1, ground floor (see map).