Here is an example of HTML code using the `rowspan` attribute:
```html
Header 1 |
Header 2 |
Header 3 |
---|
Row 1, Cell 1 |
Row 1, Cell 2 |
Row 1, Cell 3 |
Row 2, Cell 2 |
Row 2, Cell 3 |
Row 3, Cell 1 |
Row 3, Cell 2 |
Row 3, Cell 3 |
```
In this example, the `rowspan="2"` attribute is used in the first cell of the first row to span two rows. This means that the cell will take up the space of two rows in the table.