Looking for an affordable awesome weekend trip? This month, you can visit more than 100 of the nation’s most spectacular public spaces without paying admission.

In celebration of National Park Week, the 118 national parks that usually charge an entry fee will waive that fee for two weekends: April 15-16 and April 22-23.

(Of course, there are around 300 national parks that are always free, no matter the day.)

The fee waiver includes entrance fees, commercial tour fees, and transportation entrance fees, NPS notes, but other fees for things like reservations, camping, tours, concessions, and fees collected by third parties are not included unless stated otherwise.

NPS is offering a total of 10 free admission days throughout 2017 to celebrate the agency’s 100th birthday. If you can’t make it to a park this month, other no-fee days left this year include Aug. 25 (NPS’ birthday), Sept. 30 (National Public Lands Day), or Nov. 11-12 (Veterans Day weekend).

Just remember a few basic safety tips when you go: Don’t wander off designated paths, and curb your desire to take selfies with dangerous wildlife, lest you find yourself in a dangerous situation with a bison.

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