We had great weather so sat outside on the terrace, great view and ambiance. Yet the service was just not good, the waiter was very inpolite and unfriendly. The food was just horrible, my partner had the burger, which was just too well-done, and really nothing special. And I had the salmon tartar, which was even worse: worst presentation ever, and the taste was traumatic. Very sad.

Regularily having lunch at Kubu as I am working nearby.

The key positives points are:
- a really really really great burger, huge, with fries and colesaw, done on an open grill.. currently my favourite palce in Frankfurt if I want to eat a great burger
- the Wiener Schnitzel is also great as are many other dishes
- it is centrally located, big and you usually get a table without having reserved one
- in Summer it is really nice to sit outside with an view of the Opera
- Prices are ok for the quality of food

Negatives:
- Service ist not ideal, especially during lunch hours, often a beverage is forgotten or there are clarification questions 5 minutes after order has been taken
- it can happen that you have to wait for 10 minutes until you get a menu and iat happend at least three times that we had to wait for our food for c. 40 minutes, which is a no go during a lunch break

was there several times, both on business and leisure, in groups and for a "table for two", inside and on the large terrace facing Alte Oper - so really Frankfurt city centre.
Nice choice of meat and fish for the grill - so almost everybody can some great food.
Not over creative, but good quality. Friendly service. Due to the size inside & outside, sometimes a bit of a "busy" atmosphere.

Absolutely awful restaurant.
Meal not tasty, service is equal to zero.
All dishes are prepared on one base. I think that it is a problem of the cook.
It is possible to wait for waiter (waitress) for 20-30 minutes while he (she) will decide to approach and accept your order.
The prices very high.
I will not recommend visiting this restaurant.
Only the place of the restaurant is OK and also to sit and eat ice-cream in the evening and, maybe, to drink a cocktail.

We celebrated a PhD party with another couple there. The restaurant was very romantic, cozy, modern and with a nice design! In the winter during the week it was quite empty and we got all the attention of the service. The restaurant is very big and you can celebrate a big party here!
The food was delicious and you can choose also the fresh fish and meet. I had a delicious steak (26€) and my friend a lamb chops(19€) – just music of taste! In general, prices are around 10-26€ that is quite good for Frankfurt & this quality of food! Try the red wine, they have an excellent choice.
The best thing about Kubu is that everybody can find something what he going to like. I recommended this restaurant to my colleagues (group of 15 people) and almost everybody was very happy and thanked me for a such good recommendation.
I heard the Sunday brunch should be also very good. I will try it this summer for sure! Just sit outside in the garden and enjoy the good food, champagne and time with the good friends!