There's a new tourist attraction at the National Mall in Washington, D.C. ... a gigantic replica of the birthday card Donald Trump allegedly sent to Jeffrey Epstein can now be seen -- and signed -- by tourists.

As you know ... Trump reportedly drew a crude figure of a woman's naked torso on the 2003 note, which was discovered in a birthday book for the deceased convicted sex offender. Trump denied the card was from him, and is suing the Wall Street Journal, the outlet that first published the card.

The massive installation -- reportedly erected by the group known as "The Secret Handshake" -- includes the text "Happy birthday -- and may every day be another wonderful secret."

A makeshift filing cabinet, labeled "The Files" stands in front of the replica along with a box of Sharpies.

Visitors are reportedly encouraged to write on the card but warned that any "promotional, violent or hateful speech" will result in the installation's removal.

"The Secret Handshake" was previously linked to other installations ... including one featuring Trump holding hands with Epstein skipping together. The group's members have remained anonymous.