There are two large annual environmental events held in Budapest, Earth Day (officially April 22, but often celebrated on a near weekend day) and World Car Free Day (September 22). During each day, major roads are closed to motorized traffic, including Andrassy Ut, and local NGOs set up stalls with information about local and international environmental concerns, concerts, and a wide variety of children's programs. Budapest will celebrate Earth Day on Sunday, April 19th this year. <!-- pagebreak -->
Here is a sample of what is going on:

- Saturday April 18, 11am: Celebration of Composting: HuMuSz House (XI. ker. Saru utca 11.)
Sunday, April 19
- Critical Mass, see below
- Tree planting in the 12th District
- Concerts, NGO stands, etc. at the City Hall Park and Karoly Krt
- Merlin Theater: Energy Stage
- Demonstration Against Global Warming, early afternoon between Astoria and Deák tér. Come in a green shirt and join thousands of others when Brithish air photographer snaps his picture of the event from a helicopter 150m above you.
- Events at Erzsébet tér start at 10am, including a huge handicrafts and design fair organised by WAMP
- Unconfirmed, but the local authorities usually hold a household hazardous selective collection in many districts. The 6th District, if it happens, will be on Saturday from early morning until around noon at Hunyadi ter. Bring your old paint, compact florescent lightbulbs, old chemical cleaners, expired medicines, dead batteries, etc. for safe disposal.

Critical Mass is a bicycling event typically held on the last Friday of every month in over 300 cities around the world. Critical Mass-like bike tours with hundreds of participants began in Stockholm, Sweden in the early 1970s, but the first protest-type ride happened in 1992 in San Francisco. The 1992 ride was originally founded with the idea of drawing attention to how unfriendly the city was to bicyclists, and became a monthly protest by cyclists reclaiming the streets. However, in countries where Critcal Mass is held without permits or prior notification to the police, Critical Mass participants have insisted that these events should be viewed as "celebrations" and spontaneous gatherings, and not as protests or organized demonstrations.This stance allows Critical Mass to argue a legal position that its events can occur without advance notification of local police.

Many small cities have monthly Critical Mass rides. The largest events using the name Critical Mass, have happened in our own fair city. Cyclists in Budapest, Hungary hold two rides each year on April 22 (Earth Day) and September 22 (International Car Free Day). The Earth Day 2008 Budapest ride was estimated at 80,000 riders!

This Year:
Budapest, April 19, Start 3pm in the Taban Park, End 17:30 in City Park
Eger, April 22, Start 5pm, Érsekkerti Fountain
Debrecen, April 22, Start 5pm, Debreceni Nagyerdo", Békás Lake

Don't have a bike?
Yellow Zebra Bikes/Discover Budapest - Spring Bike Rental Clear Out - Over 30 bikes available from 3000 Ft a month for a 1 year old bikes! Don't want to have the hassle of buying a bike and storing it over the off season? Only need a bike for a few months? We offer cheap and reasonable solution for locals wanting a bike for the good weather times on our long term rental options. Details are available at their office or call or email. Offer valid while supplies last and from April 1st to May 31st. Treehugger Dan's Bookstore and Lounge shares space with Yellow Zebra Bikes/Discover Budapest , VI. Dist. Budapest, Lazar utca 16, Located just behind the Opera House . Tel: 269-3843 email: bookings@yellowzebrabikes.com

Background Info Source: http://en.wikipedia.org/wiki/Critical_Mass_bike_ride