October 1 is known as Tokyo Citizens’ Day (都民の日, Tomin no Hi). Although it is a regular work day, many government-run cultural institutions in the metropolitan area will be open for free. Most Tokyo public schools will have the day off.
Here are some places to visit. Please note that not all exhibitions and spaces at these venues will be open free-of-charge. Please check official websites before going, as hours, schedules, and other conditions may change. Some places require reservations.
Museums
Tokyo Metropolitan Teien Art Museum
Only the garden is open for free admission on October 1.
Phone: 03-3443-0201
https://www.teien-art-museum.ne.jp/en/
Tokyo Photographic Art Museum
Exhibitions: Chikako Yamashiro: Reframing the land/mind/body-scape, Manabu Miyazaki: Wild Animals Now, Reversible Destiny: Australian and Japanese contemporary photography
Phone: 03-3280-009
https://topmuseum.jp/e/contents/index.html
Museum of Contemporary Art Tokyo
MOT Collection Exhibition
Phone: 03-5245-4111
https://www.mot-art-museum.jp/en/
Edo-Tokyo Museum
Permanent Exhibition
Phone: 03-3626-9974
https://www.edo-tokyo-museum.or.jp/en/
Edo-Tokyo Open Air Architectural Museum
Phone: 042-388-3300
https://www.tatemonoen.jp/english/
Tokyo Metropolitan Art Museum
Exhibition: Walls & Bridges – Touching the World, Living the World
Phone: 03-3823-6921
https://www.tobikan.jp/en/index.html
Zoos/Botanical Gardens
Jindai Botanical Garden
*Reservations required
Phone: 042-483-2300
https://www.tokyo-park.or.jp/jindai/#googtrans(en)
Tama Zoological Park
*Reservations required
Phone: 042-591-1611
https://www.tokyo-zoo.net/english/tama/index.html
Ueno Zoological Gardens
*Reservations required
Phone: 03-3828-5171
https://www.tokyo-zoo.net/english/ueno/index.html
Tokyo Sea Life Park
*Reservations required
Phone: 03-3869-5152
https://www.tokyo-zoo.net/english/kasai/index.html
Inokashira Park Zoo
*Reservations required
Phone: 0422-46-1100
https://www.tokyo-zoo.net/english/ino/index.html
Yumenoshima Tropical Greenhouse Dome
Phone: 03-3522-0281
https://www.yumenoshima.jp/english.html
Tokyo Port Wild Bird Park
Phone: 03-3799-5031
http://www.wildbirdpark.jp/en/index.html
Gardens (All Require Reservations)
Hamarikyu Gardens
Phone: 03-3541-0200
https://www.tokyo-park.or.jp/park/format/index028.html
Former Shiba Rikyu Garden
Phone: 03-3434-4029
https://www.tokyo-park.or.jp/park/format/index029.html
Koishikawa Korakuen
Phone: 03-3811-3015
https://www.tokyo-park.or.jp/park/format/index030.html
Rikugien
Phone: 03-3941-2222
https://www.tokyo-park.or.jp/park/format/index031.html
Former Iwasaki House Garden
Phone: 03-3823-8340
https://www.tokyo-park.or.jp/park/format/index035.html
Mukojima Hyakkaen
Phone: 03-3611-8705
https://www.tokyo-park.or.jp/park/format/index032.html
Kiyosumi Garden
Phone: 03-3641-5892
https://www.tokyo-park.or.jp/park/format/index033.html
Old Furukawa Garden
Phone: 03-3910-0394
https://www.tokyo-park.or.jp/park/format/index034.html
Tonogayato Garden
Phone: 042-324-7991
https://www.tokyo-park.or.jp/park/format/index036.html