Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Date | Tournament | Surface | Opponent in final | Score in final |
| --- | --- | --- | --- | --- |
| April 26, 1999 | Munich , Germany | Clay | Franco Squillari | 6–4, 6–3 |
| June 14, 1999 | s’Hertogenbosch , Netherlands | Grass | Patrick Rafter | 3–6, 7–6, 6–4 |
| October 27, 2003 | Paris , France | Carpet | Tim Henman | 6–2, 7–6, 7–6 |
| April 25, 2005 | Munich, Germany | Clay | David Nalbandian | 6–4, 6–1 |
| May 22, 2006 | Portschach , Austria | Clay | Nikolay Davydenko | 6–0, 6–3 |
| July 23, 2007 | Umag , Croatia | Clay | Carlos Moyà | 6–4, 6–2 |
Question:
What is the surface of the tournament with david nalbandian as the opponent in the final?
Answer:
Clay