Bich Dong Pagoda dates from the 18th century, and features a pre-Nguyen dynasty architectural style. It’s built into a mountainside at three levels, and some shrines are inside dark caves. The steps make it easy to navigate and the views are beautiful; it was not possible for me to do them justice in photos because there’s a lot of greenery blocking them, the main perspective is almost straight up.
Word of warning: Tam Coc has the most aggressive hawkers I’ve encountered in Vietnam, and I’ve been here for two years now. The old women who sell fruit and souvenirs will literally run ahead of you and lock up the temples if you don’t buy from them. $2-6 is enough to pay for a folding fan and some bananas, come armed with small bills.