Good Chinese can be hard to find in any city. In Madrid, it’s extra difficult. You don’t just need to know the place; you need to know how to find it. For example, Zhou Yulong — widely considered to be Madrid’s best Chinese restaurant — is hidden in an underground car park in the city’s center.

But don’t think about asking for directions. No one calls the restaurant by its name. Instead it’s known as el chino secreto, el chino subterráneo or even the Blade Runner restaurant. It’s best to go with a regular; otherwise the instructions are a little confusing, like: Follow the dingy staircase to a dingy corridor. Walk past the entrance to the car park. There, opposite the industrial lift, you’ll see Zhou Yulong.

There’s no sign, no decorations. The menu sticky-taped to the window is about the only indication that it’s a restaurant. In fact, it would be easy to walk right past except for the queue of people waiting. Zhou Yulong may be notoriously difficult to find, but it’s also notoriously popular — infamous for its odd location, no-frills service and authentic Chinese dishes.

It’s food that tastes like it comes from a bustling hidey-hole in downtown Shanghai.

For Juan Ruiz, one of the locals lined up, the dishes are the main attraction. “It’s not like the food you find in other Chinese restaurants in Madrid,” he explains, where there’s a lot of fast-food or really Westernized Chinese food. That “the place is popular with Chinese people from the city also makes me think that it is more authentic,” he adds. A mix of people wait for a table: a Madrid hipster, some bored office workers and couples conversing in Mandarin.

Zhou Yulong offers dishes like dumpling soup, zongzi (a kind of pyramid rice dish wrapped in leaves) and fried rice cakes — which at first glance may seem underwhelming but are anything but, according to Ruiz. It’s not food that will win awards or appear in gastronomy magazines, but food that tastes like it comes from a bustling hidey-hole in downtown Shanghai.

I ordered “mixed stir-fried vegetables” and was delighted by an overflowing plate of glistening green beans, mushrooms and lotus root (about $4.75), followed by a steaming bowl of dumpling soup that far exceeded my expectations. As Asian pop songs played on the TV in the corner, I devoured the two giant main meals in about 10 minutes. The dishes are a thoughtful mix of tangy and spicy flavors that go beyond soy sauce. And while you don’t normally expect much for under 5 euros, the quality here is good — not get-what-you-pay-for good.

Be warned: All the waitstaff speak Mandarin only. And trying to find out information about the restaurant is like being in a film noir: No one wants to talk to you, and you can’t contact the shadowy boss figure. The staff won’t tell you his name, but they will write down your number on a Post-it note in case he wants to call you.

After numerous visits, what I learned about Zhou Yulong could be distilled into a very short list. The restaurant opened in 2000, and no one knows what time the boss comes in. While the restaurant is highly rated on Yelp and TripAdvisor, it has zero online presence: No Facebook or Instagram, no email address, no website. You could try calling the landline, but good luck having someone pick up. All has added to the restaurant’s near-mythic status.

Zhou Yulong may not be the easiest place to find, but it is certainly worth the effort.