D-tower is an art piece, commissioned by the city of Doetinchem in the Netherlands, that maps the emotions of the inhabitants of Doetinchem. D-tower records HAPPINESS, LOVE, FEAR and HATE daily using different questions.

D-tower consists of:
1. a tower, 12 metres tall, in the centre of Doetinchem
2. a website
3. a questionnaire

The D-tower project is conceived by artist Q.S. Serafijn and architect Lars Spuybroek / NOX-Architekten.

D-tower collects its information on a statistical basis. D-tower uses a questionnaire to record emotions. This questionnaire contains 360 questions. Every other day, four new questions are made available to the inhabitants of Doetinchem. An example: 'Are you happy with your partner?' Possible answers: 'very much' - 'yes' - 'a little' - 'no' - 'absolutely not' - 'not applicable'. Each answer has a score.

The answers are collected by D-tower, the scores calculated and translated into hand-drawn graphical representations. These graphs are presented on the website. Because the zipcodes of the participants are known to D-tower, the emotions of the participants can be placed on the map of Doetinchem. This allows visitors to see what street houses the happiest people in Doetinchem, where people are scared, and where love flows.

A select group of inhabitants, that have subscribed voluntarily, answer the questions. After subscribing, the participants receive a password for personal access to the questionnaire. This method ensures that the emotional condition of the city cannot be influenced by people not living in Doetinchem. The participants are from different parts (zipcode regions) of the city.

In D-tower, every emotion has its own symbolic colour: red for LOVE, blue for HAPPINESS, yellow for FEAR and green for HATE. Every day, D-tower calculates the most prominent emotion, based on the answers received by the participants. Every night, the tower in the centre of Doetinchem lights up in one of these colours. If there was a lot of HAPPINESS in the city on day 1, the tower will turn blue. If a lot of LOVE was in the air on day 2, the tower will glow up red...

Each survey lasts six months. Because D-tower presents four new questions every other day, a full round of questions and answers is completed after six months. After these months, the survey restarts with new participants and a six month duration. The results are archived per day and month, and can be viewed on the website.

Besides the survey, D-tower offers functionality for communication and exchange. Visitors and participants can publish a letter on on http://www.d-toren.nl, or exchange thoughts with others on various subjects. These 'dialogues' are placed on the website.